-NRLF 


GIFT   OF 
Mr.   George  N,   Brewer 


-  - 


"  He  telleth  the  number  of  the  Stars,  and  calleth  them  all  by  ther*  numes. 


THE 


GEOGRAPHY  OF  THE  HEAVENS, 


AND 


CLASS-BOOK  OF  ASTRONOMY: 

ACCOMPANIED  BY 

A  CELESTIAL  ATLAS 

BY    ELIJAH    H.    BIJRRITT,    A.M. 

QREATLY     ENLARGED,     REVISED     AND     ILLUSTRATED, 

tfY  H.  MATTISON,  A.  M. 

NEW     AND     REVISED     EDITION. 


NEW    YORK: 
MASON"   BROTHERS,   596 

BOSTON:  154  TKEMONT  ST. 


Entered  according  to  Act  of  Congress,  in  the  year  1856,  by 

V.  .1.  HUNTINGTON, 

In  me  Clerk's  Office  of  the  District  Court  of  the  United  States  for  tli.  Southern 
District  of  New  York. 


ALVORD,    PRINTER. 


PREFACE. 


THE  rapid  progress  of  the  science  of  astronomy,  for  the  liwr. 
"few  years,  has  again  rendered  it  necessary  to  revise  the  Geo- 
graphy of  the  Heavens — a  work,  the  popularity  of  which  is  suffi- 
ciently proved  by  a  sale  of  300,000  copies.  The  editor  has, 
therefore,  availed  himself  of  the  occasion  to  make  such  improve- 
ments, both  in  the  book  and  maps,  as  seemed  to  be  demanded  by 
the  progress  of  the  science,  and  the  most  approved  methods  of 
instruction.  Among  these  improvements  we  may  mention  the 
following  : — 

1.  The  matter  of  the  book  has  been  thoroughly  assorted  ;  the 
most   important  paragraphs  being  printed  in  large   type,  and 
numbered,  as  in  most  modern   text-books  ;    while   that  which 
seemed  in  the  main  explanatory  of  the  more  important  portions, 
is  left  in  small  print.     By  this  means  an  agreeable  variety  is 
afforded  to  the  eye,  while  the  book  is  made  to  contain  far  more 
matter,  and  is,  consequently,  far  more  complete,  than  it  could 
otherwise  have  been. 

2.  A  new  set  of  Questions  has  been  prepared  throughout. 
These   are   brief,    topical   and   suggestive  ;    and   numbered   to 
answer  to  the  paragraphs  to  which  they  relate. 

3.  A  complete  list  of  Telescopic  Objects  in  each  constellation 
has  been  inserted  ;  giving  the  Right  Ascension  and  Declination 
of  each  object ;  with  a  brief  description  of  it  ;  and  easy  land- 
marks and  directions  by  which  it  may  be  found  ;  and  references 
to  telescopic  views  of  the  same  in  the  new  maps.     The  color  and 
relative  magnitude  of  the  components  of  the  double  stars,  are 
also  given.     These  Telescopic  Objects,  compiled  with  great  labor 
from  Smyth^  Cycle,  of  Celestial  Oljects,  will  be  found  especially 

M530304 


IV  PREFACE. 

valuable  to  all  institutions  having  an  equatorial  telescope 
Indeed,  they  greatly  enhance  the  value  of  the  work  for  al 
classes  of  students. 

4.  Several  small  constellations  that  were  delineated  on  thp 
maps,  but  were  not  described  in  former  editions  of  the  book, 
have  been  described,  and  their  history  given  in  the  present, 
edition. 

5.  The  page  of  the  book  has  been  greatly  enlarged,  for  the 
double  purpose  of  printing  more  matter  and  in  larger  type  : 
and  to  afford  scope  for  wood-cut  illustrations.     Of  these,  great 
numbers  have  been  introduced  into  the  second  part  of  the  work, 
adapting  it,  in  this  respect  also,  to  the  wants  of  both  teacher 
and  student. 

6.  Still  further  to  illustrate  the  second  part  of  the  work,  the 
first  map  of  the  atlas  has  been  re-drawn  and  re-engraved,  so  as 
to  illustrate  more  and  better  than  the  old  map. 

7.  Two  entirely  new  maps  have  been  introduced  into  the  Atlas, 
containing  views  of  eighty  different  celestial  objects  ;  such  as 
Double    Stars,    Clusters,    Nebulae,    Comets,    &c.      These    are 
all  referred  to  in  the  book,  and  in  turn  refer  from  the  objects 
back  to  the  page  of  the  book  where  they  are  described.     These 
maps  and  the  corresponding  descriptions  in  the  book  will  be 
found  not  only  extremely  interesting,  but  of  incalculable  value 
to  the  student. 

8.  A  chapter  on  the  history,  structure  and  use  of  Telescopes, 
Transit  Instruments,  &c.,  has  been  introduced — a  subject  which 
every  student  of  astronomy  should  understand,  but  one  to  whicb 
no  attention  was  given  in  the  previous  editions. 

Such  are  some  of  the  principal  new  features  of  the  present 
edition — larger  type,  new  questions,  telescopic  objects,  new  maps, 
new  matter,  and  numerous  illustrations,  making  it  the  most  per- 
lect  and  complete  text-book  of  astronomy  ever  offered  to  the 
American  public. 

H.  MATTISON 

New  Yorlc,  July  18G6. 


INDEX    TO    THE    CONSTELLATIONS. 


Andromeda 
Antinoua         .. 
Anser  et  Velpecula 
Aries      ... 
Argo  Navis 


PACK 

18 

...    118 
.        .        .121 

.      28 
62 
Aquila     .......    118 

Aquarius        ......    131 

Auriga    .        .        .      '  .        .        .        .49 

Bootes    .......      84 

Cainelopardalus     .....      51 

Oaucer    .......64 

Janes  Venatici      .....      83 

Canis  Major   ......      59 

Canis  Minor  ......      56 

Cupricornqs   ......     121 

Cassiopeia      ......      22 

Centaurus      ......      88 

Cepheus          ......      25 

Cetus      .......      32 

Columba         ......      46 

Coma  Berenices    .....      77 

Corvus    .......      78 

Corona  Australis    .....     118 

Corona  Boreali*  ....      94 

Crater    .  ....      71 

Cygnus  ......        .124 

Delphinus       .        .        .  .        .122 

Draco     .......     110 

Eridanus         ......      47 

Equuleus         .    '    .....    131 

Gemini    .......      53 

Gloria  Frederica    .  .134 

Hercules  .     103 


Lynx 
Lyra 

Monoceros 
Musca    . 


Hydra 71 

Lacerta 134 

Leo 66 

Leo  Minor 69 

Lupus  (The  Wolf)          ....  90 

Lepus  (The  Hare)          ....  45 

Libra 91 

52 

112 

58 

82 

Nocta 83 

Ophiuchus 107 

Orion 41 

Pegasus 129 

Perseus  .        .        .        .        .        .        .35 

Pisces 20 

Pisces  Australis     .        .                .        .  166 

Sagittarius     ...                         .  116 

Sagitta 121 

Scutum  Sobieski lib' 

Scorpio 100 

Sceptrum  Braudenburgium  ...  49 

Serpentarius  vel  Ophiuchus          .        .  107 
Serpens  .        .        .               *        .        .93 

Sextans 70 

Taurus 38 

Taurus  Poniatowski      .        .        .        .115 

Telescopium  llerschellii        ...  53 

Triangulae      ......  31 

Ursa  Major 73 

Ursa  Minor 96 

Virgo 80 


CONTENTS. 


PART    I.  -THE   CONSTELLATIONS. 


r.tr.u 

CHAPTER  I.  Constellations  on  the  meridian  in  November,                   *        •        • 

18 

44         II. 

December,           .... 

23 

«    m.       ••        "-      " 

January,              .... 

38 

it         iy                  u                   u                tt 

February,             .... 

52 

14                y^                         U                            41                         II 

March,                  .... 

62 

u          VI.                  "                    "                 '* 

April,                    .        . 

66 

"      VIL             "               "             " 

May,                    .       .       .       ^ 

73 

u    vill. 

June,                    .... 

84 

44       IX. 

July,                     .... 

100 

44         X. 

August,                 .... 

110 

ti         xi.                  u                    u                 it 

September,          .... 

122 

u      XII.                 "                   "                " 

October,               .... 

129 

u   XIII.  Variable  and  Double  Stars—  Clusters  and  Nebulae,    .... 

135 

"    XIV.  Via  Lactea,  or  Milky-  Way 

141 

"     XV.  Origin  of  the  Constellations, 

........ 

143 

"    XVI.  Number,  Distances  and  Econc. 

148 

"   XVII.  Falling,  or  Shooting  Stars,          .        .        .        .        .        .        . 

154 

PART     II.  -THE     SOLAR     SYSTEM. 

CHAPTER  I.  General  Phenomena  of  the  Solar  System,  History,  Ac.,    .        .  163 

"        H.  The  Sun—  His  Distance,  Magnitude,  Ac.,            .....  171 

**      HI.  The  Primary  Planets  —  Mercury,  Venus,  Ac.,    .....  177 

"       IV.  The  Moon—  Her  Distance,  Motions,  Phases,  Ac.,      ....  203 

*         V.  Solar  and  Lunar  Eclipses,  .........  214 

"       VI.  Primary  Planets  continued  —  Mars  and  the  Asteroids,       .        .        .  224 

"     VII.  Primary  Planets—  Jupiter  and  Saturn,        .....        .  233 

«•   Vni.  Primary  Planets—  Uranus  and  Neptune,    ....                .  245 

'«      IX.  Comets—  Their  Nature,  Motions,  Orbits,  Ac.,     .....  249 

"       X.  Of  the  Forces  by  which  the  Planets  are  retained  in  their  Orbits,   '  .  2C2 

"      XI.  Proper  Motion  of  the  Sun  in  Space,    .......  268 

"    XII.  Precession  of  the  Equinoxes—  Obliquity  of  the  Ecliptic,  .        .        .210 

"  XIII.  Philosophy  of  the  Tides,      .........  280 

"  XIV.  The  Seasons—  Different  Lengths  of  the  Days  and  Nights,          .        .  287 

"    XV.  The  Harvest  Moon,  and  Horizontal  Moon,         .....  293 

"   XVI.  Refraction  and  Twilight,     .........  297 

•'  XVII.  Aurora  Borealis  and  Parallax,     ........  302 

"XVIII.  Practical  Astronomy—  Reflection  and  Rel  action  of  Light,      .        .  308 

"   XIX.  Refractors  and  Rejectors,           ...        .....  813 

M     XX.  Problems  and  Tables,    ....  33J 


INTRODUCTION 


1.  ASTRONOMY  is  the  science  of  the  heavenly  bodies — the  Sun, 
Moon,  Planets,  Comets,  and  Fixed  Stars. 

2.  In  entering  upon  this  study,  the  phenomena  of  the  hea- 
vens, as  they  appear  on  a  clear  evening,  are  the  first  objects  that 
demand  our  attention.     Our  first  step  is  to  learn  the  names  and 
positions  of  the  heavenly  bodies,  so  that  we  can  identify,  and 
distinguish  them  from  each  other. 

In  this  manner  they  were  observed  and  studied  ages  before  books  were  written,  and  it 
was  only  after  many  careful  and  repeated  observations,  that  systems  and  theories  of 
Astronomy  were  formed.  To  the  visible  heavens,  then,  the  attention  of  the  pupil  should 
be  first  directed,  for  it  is  only  when  he  shall  have  become,  in  some  measure,  familiar 
with  them,  that  he  will  be  able  to  locate  his  Astronomical  knowledge,  or  fully  compre- 
hend the  terms  of  the  science. 

3.  For  the  sake  of  convenient  reference,  the  heavens  were 
early  divided  into  constellations,  and  particular  names  assigned 
to  the  constellations  and  to  the  stars  which  they  contain.     A 
constellation  may  be  defined  to  be  a  cluster  or  group  of  stars 
embraced  in  the  outline  of  some  figure.     These  figures  are,  in 
many  cases,  creations  of  the  imagination  ;  but  in  others,  the 
stars  are  in  reality  so  arranged  as  to  form  figures  which  have 
some  resemblance  to  the  objects  whose  names  have  been  assigned 
to  them. 

These  divisions  of  the  celestial  sphere  bear  a  striking  analogy  to  the  civil  divisions  of 
the  globe.  The  constellations  answer  to  states  and  kingdoms,  the  most  brilliant  clus- 
ters to  towns  and  cities,  and  the  number  of  stars  in  each,  to  their  respective  population. 
The  pupil  cap  trace  the  boundaries  of  any  constellation,  and  name  all  its  stars,  one  by 
one,  as  readily  as  he  can  trace  the  boundaries  of  a  state,  or  name  the  towns  and  cities 
from  a  map  of  New  England.  In  this  sense,  there  may  be  truly  said  to  be  a  Geography 
of  the  Heavens. 

4.  The  stars  are  considered  as  forming,  with  reference  to 

1.  What  is  Astronomy?  2.  What  first  studied?  First  step?  3.  How  are  t^ie 
heavens  divided,  and  why?  What  is  a  constellation  ?  Wh.it  of  these  figures  ?  Iu  what 
sense  may  there  really  be  a  "  Geography  of  the  heaventV  4.  How  are  the  star-j 
classified,  as  respects  their  magnitude?  What  expedient  for  uesignatiu 5  their  places 
tu  the  heavens? 


10  ASTRONOMY. 

their  magnitudes,  sixteen  classes  ;  the  brightest  being  called 
stars  of  the  first  magnitude,  the  next  brightest,  stars  of  the 
second  magnitude,  and  so  on  to  the  sixth  class,  which  consists 
of  the  smallest  stars  visible  to  the  naked  eye.  The  next  ten 
classes  are  seen  only  through  telescopes. 

In  order  to  be  able  to  designate  with  precision  their  situa- 
tions, imaginary  circles  have  been  considered  as  drawn  in  the 
heavens,  most  of  which  correspond  to,  and  are  in  the  same  plane 
with,  similar  circles,  supposed  for  similar  purposes,  to  be  drawn 
on  the  surface  of  the  Earth. 

5.  In  order  to  facilitate  the  study  of  Astronomy,  artificial 
representations  of  the  heavens,  similar  to  those  of  the  surface  of 
the  Earth,  have  been  made.     Thus,  a  Celestial  Atlas,  composed 
of  several  maps,  accompanies  this  work.     Before,  however,  pro- 
ceeding to  explain  its  use,  it  is  necessary  to  make  the  pupil 
acquainted  with  the  imaginary  circles  alluded  to,  called  the  Cir- 
cles of  the  Sphere. 

CIRCLES  OF  THE  SPHERE. 

6.  The  Axis  of  the  Earth  is  an  imaginary  line,  passing  through 
its  centre,  north  and  south,  about  which  its  diurnal  revolution  is 
performed. 

The  Poles  of  the  Earth  are  the  extremities  of  its  axis. 

The  Axis  of  the  Heavens  is  the  axis  of  the  Earth  produced 
both  ways  to  the  concave  surface  of  the  heavens. 

The  Poles  of  the  Heavens  are  the  extremities  of  their  axis. 

The  Equator  of  the  Earth  is  an  imaginary  great  circle  pass- 
ing round  the  Earth,  east  and  west,  everywhere  equally  distant 
from  the  poles,  and  dividing  it  into  northern  and  southern  hemi- 
bpheres. 

The  Equator  of  the  Heavens,  or  Equinoctial,  is  the  great  circle 
formed  on  the  concave  surface  of  the  heavens,  by  producing  the 
plane  of  the  Earth's  equator. 

A  plane  is  that  which  has  surface  but  not  thickness.  The  plane  of  a  circle  is  that  ima- 
ginary superficies  which  is  bounded  by  the  circle. 

7.  The  Rational  Horizon  is  an  imaginary  great  circle,  whose 
plane,  passing  through  the  centre  of  the  Earth,  divides  the  hea- 
vens into  two  hemispheres,  of  which  the  upper  one  is  called  the 

5.  What  helps  to  facilitate  the  study  of  the  heavens?  Circles?  Called  what? 
6.  Axis  of  the  Earth ?  Poles?  Axis  of  the  heavens?  Poles  of  the  heavens?  Equator 
of  the  Earth  ?  Equator  of  tha  heavens,  or  Equ  noctial  ?  7.  Rational  horizon  ?  Sensi- 
ble or  apparent  f 


CHICLES    OF    THE    SPHERE.  II 

visible  hemisphere,  and  the  lower  one,  the  invisible  hemisphere. 
It  is  the  plane  of  this  circle  which  determines  the  rising  and  set- 
ting of  the  heavenly  bodies. 

The  Sensible  or  Apparent  Horizon,  is  the  circle  which  termi- 
nates our  view,  where  the  Earth  and  sky  appear  to  meet. 

To  a  person  standing  on  a  plain,  this  circle  is  but  a  few  miles  in  diameter.  If  the  eye 
he  elevated  five  feet,  the  radius  of  the  sensible  horizon  will  be  less  than  two  miles  and 
three  quarters ;  if  the  eye  be  elevated  six  feet,  it  will  be  just  three  miles.  The  observer 
being  always  in  the  centre  of  the  sensible  horizon,  it  will  move  as  he  moves,  and  enlarge 
or  contract,  as  his  station  is  elevated  or  depressed. 

8.  The  Poles  of  the  Horizon  are  two  points,  of  which  the  one  is 
directly  overhead,  and  is  called  the  Zenith  ;  the  other  is  directly 
underfoot,  and  is  called  the  Nadir. 

Vertical  Circles  are  circles  drawn  through  the  Zenith  and 
Nadir  of  any  place,  cutting  the  horizon  at  right  angles. 

The  Prime  Vertical  is  that  which  passes  through  the  east  and 
west  points  of  the  horizon. 

9.  The  Ecliptic  is  the  plane  of  the  Earth's  orbit ;  or  the  great 
circle  which  the  Sun  appears  to  describe  annually  among  the 
stars.     It  crosses  the  Equinoctial,  a  little  obliquely,  in  two  oppo- 
site points,  which  are  called  the  Equinoxes.     The  Sun  rises  in 
one  of  these  points  on  the  21st  of  March  ;  this  point  is  called 
the  Vernal  Equinox.     It  sets  in  the  opposite  point  on  the  23d 
of  September  ;  this  point  is  called  the  Autumnal  Equinox.    One 
half  of  the  Ecliptic  lies  on  the  north  side  of  the  Equinoctial,  the 
other  half  on  the  south  side,  making  an  angle  with  it  of  23£°. 
This  angle  is  called  the  obliquity  of  the  Ecliptic.     The  axis  of 
the  Ecliptic  makes  the  same  angle  with  the  axis  of  the  heavens; 
so  that  the  poles  of  each  are  23-j-0  apart. 

This  angle  is  perpetually  decreasing.  At  the  commencement  of  the  Christian  era,  it 
was  about  23*  45'.  At  the  beginning  of  1836,  it  was  oniy  23*  27'  88",  showing  an  annual 
diminution  of  about  half  a  second,  or  46".70  in  a  hundred  years.  A  time  will  arrive, 
however,  when  this  angle,  having  reached  its  minimum,  will  again  increase  in  the  same 
ratio  that  it  had  before  diminished,  and  thus  it  will  continue  to  oscillate  at  long  periods, 
between  certain  limits,  which  are  said  to  be  comprised  withiu  the  space  of  20°  42'. 

10.  The  Ecliptic,  like  every  other  circle,  contains  360°,  and  it 
irf  divided  into  12  equal  arcs  of  30°  each,  called  signs,  which  the 
ancients  distinguished  by  particular  names.    This  division  com- 
mences at  the  vernal  equinox,  and  is  continued  eastwardly  round 
to  the  same  point  again  in  the  following  order :  Aries,  Taurus, 
Gemini,  Cancer,  Leo,  Virgo,  Libra,  Scorpio,  Sagittarius,  Capri- 

8.  Poles  of  the  horizon?  Vertical  circles?  Prime  Vertical ?  9.  Ecliptic?  Equi- 
noxes? How  is  the  Ecliptic  situated  with  respect  to  the  Equinoctial?  Obliquity  of 
Ecnptic?  Is  this  angle  permanent?  10.  How  is  the  Ecliptic  divided?  Where  com- 
UM-uced,  and  how  reckoned?  Name  sigl  3  in  order  ?  How  does  the  Sun  proceed  tb:  ,ugu 
Ih.  signs? 

1* 


12  ASTRONOMY. 

COTIUS,  Aquarius,  Pisces.  The  Sun,  commencing  at  the  first 
degree  of  Aries,  about  the  21st  of  March,  passes,  at  a  mean 
rate,  through  one  sign  every  month. 

11.  The  Zodiac  is  a  zone  or  girdle,  about  16  degrees  in  breadth, 
extending  quite  round  the  heavens,  and  including  all  the  heavenly 
bodies  within  8°  on  each  side  of  the  ecliptic.     It  includes,  also, 
the  orbits  of  all  the  planets,  except  some  of  the  asteroids,  since 
they  are  never  seen  beyond  8°  either  north  or  south  of  the  ecliptic. 

12.  Parallels  of  Latitude,  are  small  circles  imagined  to  be 
drawn  on  the  Earth's  surface,  north  and  south  of  the  equator, 
and  parallel  to  it. 

Parallels  of  Declination  are  small  circles,  imagined  to  be  drawn 
on  the  concave  surface  of  the  heavens,  north  and  south  of  the 
equinoctial,  and  parallel  to  it ;  or  they  may  be  considered  as 
circles  formed  by  producing  the  parallels  of  latitude  to  the 
heavens. 

13.  The  Tropic  of  Cancer  is  a  small  circle,  which  lies  23£° 
north  of  the  Equinoctial,   and  parallel   to  it.     The    Tropic  of 
Capricorn  is  a  small  circle,  which  lies  23^-°  south  of  the  Equi- 
noctial,  and  parallel  to  it.     On  the  celestial  sphere,  these  two 
circles  mark  the  limits  of  the   Sun's  farthest  declination,  north 
and  south.     On  the  terrestrial  sphere,  they  divide  the  torrid  from 
the  two  temperate  zones.     That   point  in   the   ecliptic  which 
touches  the  tropic  of  Cancer,  is  called  the  Summer  Solstice  ;  and 
that  point  in  the  ecliptic  which  touches  the  tropic  of  Capricorn, 
is  called  the  Winter  Solstice. 

The  distance  of  these  two  points  from  the  equinoctial,  is  always  equal  to  the  obliquity 
of  the  ecliptic,  which,  in  round  numbers,  is  23c° ;  but,  as  we  have  seen,  the  obliquity  of 
the  ecliptic  is  continually  changing;  therefore  the  position  of  the  tropics  must  make  ;» 
correspondent  change. 

14.  The  Colures  are  two  great  circles  which  pass  through  the 
poles  of  the  heavens,  dividing  the  ecliptic  into  four  equal  parts, 
and  mark  the  seasons  of  the  year.     One  of  them  passes  through 
the  equinoxes, at  Aries  and  Libra,  and  is  thence  called  the  Equi- 
noctial Colure;  the  other  passes  through  the  solstitial  points  or 
the  points  of  the  Sun's  greatest  declination  north  and  south,  and 
is  thence  called  the  Solstitial  Colure. 

The  Sun  is  in  the  equinoctial  points  the  21st  of  March  and  the  23d  of  September.  He 
£  in  the  solstitial  points  the  22d  of  June  and  the  22d  of  December. 

15.  The  Polar  Circles  are  two  small  circles,  each  about  66|° 


11. (.What  is  the  Zodiac?  12.  Parallels  of  latitude?  Of  declination?  ]R.  Th<? 
tropics?  Cancer?  Capricorn?  What  do  these  circles  mark  in  the  celestial  sphere* 
O;k  % ••>  terrestrial  ?  14.  The  Colures?  Where  situated  ?  When  is  the  Sun  at  the  eqm- 
Loetia,  K  '-its?  The  solsticial?  15.  What  are  the  Polar  Circles? 


CIRCLES    OF    THE    SPHERE.  13 

from  the  equator,  being  always  at  the  same  distance  from  the  poles 
that  the  tropics  are  from  the  equator.  The  northern  is  called 
the  Arctic  circle,  and  the  southern  the  Antarctic  circle. 

16.  Meridians  are  imaginary  great  circles  drawn  through  the 
poles  of  the  world,  cutting  the  equator  and  the  equinoctial  at 
right  angles. 

Every  place  on  the  Earth,  and  every  corresponding  point  in  the  heavens,  is  considered 
as  having  a  meridian  passing  through  it;  although  astronomers  apply  but  24  to  the 
heavens,  thus  dividing  the  whole  concave  surface  into  24  sections,  each  15*  in  width. 
These  meridians  mark  the  space  which  the  heavenly  bodies  appear  to  describe,  every 
hour,  for  the  24  hours  of  the  day.  They  are  thence  sometimes  denominated  Hour  Circles. 

In  measuring  distances  and  determining  positions  on  the  Earth,  the  equator  and  some 
fixed  meridian,  as  that  of  Greenwich,  contain  the  primary  starting  points;  in  the  hea- 
vens these  points  are  in  the  ecliptic,  the  equinoctial,  and  that  great  meridian  which 
passes  through  the  first  point  of  Aries,  called  the  equinoctial  colure. 

17.  Latitude  on  the  Earth,  is  distance  north  or  south  of  the 
equator,  and  is  measured  on  the  meridian. 

Latitude  in  the  Heavens,  is  distance  north  or  south  of  the  eclip- 
tic, and  at  right  angles  with  it. 

Longitude  on  the  Earth,  is  distance  either  east  or  west  from 
some  fixed  meridian,  measured  on  the  equator. 

Longitude  in  the  Heavens,  is  distance  east  from  the  first  point 
of  Aries,  measured  on  the  ecliptic. 

18.  Declination  is  the  distance  of  a  heavenly  body  either  north 
or  south  of  the  equinoctial,  measured  on  a  meridian. 

Right  Ascension  is  the  distance  of  a  heavenly  body  east  from 
the  first  point  of  Aries,  measured  on  the  equinoctial. 

It  is  more  convenient  to  describe* the  situation  of  the  heavenly  bodies  by  their  decli- 
nation and  right  ascension,  than  by  their  latitude  aud  longitude,  since  the  former  cor- 
responds to  terrestrial  latitude  and  longitude. 

Latitude  and  declination  may  extend  90°  and  no  more.  Terrestrial  longitude  may 
extend  ISO*  either  east  or  west;  but  celestial  longitude  and  right  ascension,  being  reck- 
oned in  only  one  direction,  extend  entirely  round  the  circle,  or  360°. 

It  is  easy  to  convert  ripht  ascension  into  time,  or  fine  into  right  ascension,  foi  if  a 
heavenly  body  is  one  hou:  in  passing  over  15°,  it  will  be  one  fifteenth  of  an  hour,  or  four 
minutes,  in  passing  over  1*. 

If  the  first  point  of  Aries  be  on  the  meridian  at  12  o'clock,  the  next  hour  line,  whicn 
is  15"  E.  of  it,  will  cqme  to  the  meridian  at  1  o'clock;  the  second  hour  line  at  2  o'clock; 
the  third  at  3,  &c.  Of  any  two  bodies  whose  right  ascensions  are  given,  that  one  will 
pass  the  meridian  Jirat  which  has  the  least  right  ascension. 

19.  In  consequence  of   the  Earth's   motion  .eastward  in  its 
orbit,  the  stars  seem  to  have  a  motion  westward,  besides  their 
apparent  diurnal  motion  caused  by  the  Earth's  revolution  on  its 
axis  ;  so  that  they  rise  and  set  sooner  every  succeeding  day  by 
about   four  minutes,   than  they  d:d  on  the  preceding.     This  is 

16.  Meridians?  How  many?  What  other  name?  How  measure  distances  on  the 
earth?  In  the  heavens?  17.  What  is  latitude  on  the  earth?  In  the  heavens? 
Longitude  on  the  earth?  In  the  heavens?  13.  Declination  ?  Right  ascension 
Why  describe  by  I),  and  R.  A.?  Extent  of  latitude?  Declination?  Longitude  and  R 
A  ?  flow  convert  R.  A.  into  time?  Which  of  two  bodies  given  will  first  pass  the  meri- 
Jian?  19  What  a 'parent  motion  of  stars?  Cause  ?  Results?) 


14  ASTRONOMY. 

called  their  daily  acceleration.  It  amounts  to  just  two  hours  a 
month.  On  this  account  we  have  not  always  the  same  constel- 
lations visible  to  us  throughout  the  year.  While  some,  that  were 
not  visible  before,  are  successively  rising  to  view  in  the  east,  and 
ascending  to  the  meridian,  others  sink  beneath  the  western 
horizon,  and  are  seen  no  more,  until,  having  passed  through  the 
lower  hemisphere,  they  again  reaopear  in  the  east. 


DESCRIPTION  AND  USE  OF  THE  MAPS. 

20.  THE  first  map  of  the  atlas  represents,  upon  a  large  scale, 
n  general  view  of  the  solar  system.     This  will  be  more  fully 
described  in  the  second  part  of  the  work. 

The  next  six  maps  represent  different  sections  of  the  concave 
surface  of  the  heavens.  The  first  of  these  exhibits  the  principal 
constellations  visible  to  us  in  October,  November,  and  Decem- 
ber ;  the  second,  those  visible  in  January,  February,  and  March; 
the  third,  those  visible  in  April,  May,  and  June  ;  and  the  fourth, 
those  visible  in  July,  August,  and  September  ;  with  the  excep- 
tion, however,  of  the  constellations  which  lie  beyond  the  50th 
degree  of  north  and  south  declination,  of  which,  indeed,  those 
around  the  North  Pole  are  always,  and  those  around  the  South 
Pole,  never  visible  to  us. 

21.  These  constellations  are  represented  on  the  sixth   and 
seventh  maps,  called  circumpolar  maps,  which  are  an  exact  con- 
tinuation of  the  others,  and  if  joined  to  them  at  their  correspond- 
ing degrees  of  right  ascension  and  decimation,  they  might  be 
considered  as  constituting  one  map.     The  scale  on  which  all  the 
above-mentioned  maps  are  drawn   is  that  of  a  16-inch   globe. 
The  lines  drawn  on  the  maps  have  been  already  defined  ;  and 
their  use,  being  nearly  the  same  with  those  in  geography,  will 
be  readily  understood.     Those  which  are  drawn  from  right  to 
left,  on  each  side  of  the  equinoctial  and  parallel  to  it,  are  called 
Parallels  of  Declination.     Those  which  are  drawn  up  and  down 
through  the  maps,  at  intervals  of  15°,  are  called  Meridians  of 
Right  Ascension,  or  Hour  Circles. 

The  scale  at  the  top  and  bottom  of  the  first  four  maps,  and  in  the  circumference  o;* 
the  circumpolar  maps,  indicates  the  daily  progress  of  the  stars  in  right  ascension,  and 
shows  on  what  day  of  the  month  any  star  will  be  on  the  meridian  at  9  o'clock  in  tht 
evening. 


20.  What    said    of   maps?     First?    Next    six?        21.  Sixth    and   seventh?    Scale? 
Describe  lines?    S-ale  indicates  what? 


CLASSIFICATION    OF    STARS,    NEBLL^E,    ETC.  15 

22.  The  first  four  maps  of  the  heavens  are  so  constructed 
that  the  pupil  in  using  them  must  suppose  himself  to  face  the 
south,  and  to  hold  them  directly  overhead  in  such  manner  that 
the  top  of  the  map  shall  be  towards  the  north,  and  the  bottom 
towards  the  south  ;  the  right  hand  side  of  the  map  will  then  be 
west,  and  the  left-hand  east.  In  using  the  circumpolar  maps  he 
must  suppose  himself  to  face  the  pole,  and  to  hold  them  in  such 
a  manner  that  the  day  of  the  given  month  shall  be  uppermost. 

The  constellation  called  the  Great  Bear  is  ~  exception  to  this  rule;  in  this  constel- 
lation the  principal  stars  are  marked  in  the  order  of  their  right  ascension. 

That  point  of  projection  for  the  maps  which  would  exhibit  each  successive  portion  of 
the  heavens  directly  overhead  at  9  o'clock  in  the  evening,  was  chosen,  because  in  sum- 
mer at  an  earlier  hour  the  twilight  would  bedim  our  observation  of  the  stars,  and  a». 
other  seasons  of  the  year  it  is  easier  to  look  up  to  stars  that  want  an  hour  of  their 
meridian  altitude  than  to  those  which  are  directly  overhead. 


CLASSIFICATION  OF  STARS,  NEBULA  &c. 

23.  FOR  purposes  of  convenience  in  finding  or  referring  to  par- 
ticular stars,  recourse  is  had  to  a  variety  of  artificial  methods 
of  classification.  First,  the  whole  concave  of  the  heavens  is 
divided  into  sections  or  groups  of  stars,  of  greater  or  less  extent, 
called  Constellations. — (Of  the  origin  of  these  figures  see  page 
143).  Next,  they  are  classified  according  to  their  magnitudes, 
(as  already  stated  art.  4),  and  designated  on  the  maps  accord- 
ingly. Thirdly,  the  stars  of  each  constellation  are  classified 
according  to  their  magnitudes  in  relation  to  each  other,  and  with- 
out reference  to  other  constellations.  Thus,  for  instance,  the 
largest  star  in  Taurus  is  marked  a,  Alpha  ;  the  next  largest  /?, 
Beta;  the  next,  j,  Gamma,  &c.,  till  the  Greek  alphabet  is 
exhausted.  Then  the  Roman  (or  English)  is  taken  up,  and 
finally,  if  necessary,  recourse  is  had  to  figures. 

This  useful  method  of  designating  particular  stars  by  the  use  of  the  Greek  and  Roman 
alphabet,  was  invented  by  John  Bayer,  of  Augsburg,  in  Germany,  in  1603.  It  has  been 
adopted  by  all  succeeding  astronomers,  and  extended  by  the  addition  of  the  Arabic 
notation  1,  2,  8,  &c.,  wherever  the  stars  in  a  constellation  outnumber  both  alphabets. 

As  Greek  letters  so  frequently  occur  in  catalogues  and  maps  of  the  stars  and  on  the 
celestial  globes,  the  Greek  alphabet  is  here  introduced  for  the  use  of  those  who  are 
unacquainted  with  it.  The  capitals  are  seldom  used  for  designating  the  stars,  but  are 
here  given  for  the  sake  of  regularity. 


22.  How  use  the  first  four  maps  of  the  hear  ens?  Circumpolar?  What  exception? 
What  point  of  projection  chosen,  and  why?  23  Classification  or  designation  of 
i*tars?  By  whom  invented,  and  when? 


16  ASTRONOMY. 


THE  GREEK  ALPHABET. 

A  a  Alpha  N  v  Nu 

li  /?  Beta  S  ,c  Xi 

F  y  Gamma  O  o  Omicron 

A  <5  Delta  II  •*  Pi 

E  e  Epsilon  P  p  Rho 

Z  C  Zeta  2  f  Sigma 

H  T]  Eta  T  T  Tau 

6  e  Theta      ^  Y  v  Upsilon 

I  t  Iota  $  (/>  Phi 

K  K  Kappa  X  j  Chi 

A  A  Lambda  •                 *  V'  Psi 

M  /*  Mu  •    Q  w  Omega 

24  As  a  further  aid  in  finding  particular  stars,  and  especially 
in  determining  their  number,  and  detecting  changes,  should  any 
occur,  catalogues  of  the  stars  have  been  constructed,  one  of 
which  is  over  two  thousand  years  old.  Several  of  the  principal 
stars  have  specific  names,  like  the  planets,  as  Sirius,  Aldebaran, 
Regulus,  <fcc. 

25.  The  stars  are  still  further  distinguished,  as  single,  double, 
triple,  multiple,  Unary,  variable,  'new,  ami  nebulous. 

A  single  star  is  one  that  appears  as  a  unit  under  the  most 
powerful  telescopes.  Double,  triple,  and  multiple  stars,  are  those 
that  appear  single  to  the  naked  eye,  but  by  the  aid  of  telescopes 
are  found  to  consist  of  two  or  more  stars.  Binary  stars  are 
double  stars  revolving  around  each  other,  often  called  Binary 
Systems.  Variable  stars  are  those  that  are  found  to  undergo 
certain  fluctuations  in  their  brightness,  sometimes  becoming  quite 
invisible.  In  most  cases  these  changes  are  periodical  and 
regular,  on  which  account  they  are  called  Periodical  stars. 
New  stars  are  those  that  suddenly  blaze  forth  in  some  portion 
of  the  heavens  previously  void.  Nebulous  stars  are  those  which 
are  surrounded  by  a  faint  nebula,  or  halo  of  light  or  mist. 

26.  A  duster  of  stars  is  an  assemblage  or  Jronp,   thrown 
promiscuously  together,  like  the  fflgiides  and  Hyades  in  Taurus, 
and  the  Bee  Hire  in  Cancer.     Ko'iNebiita  is  a  cluster  so  remote 
as  to  appear  only  like  a  faint  cloud  *orr  hsfate  of.  light.     Resolvable 
Nebula,  are  those  that  can  be  resolved9j$fco  distinct  stars  by  the 
aid  of  a  telescope.     Irresolvable  Nebulce  are  those  that  have  not 


24.  What  further  aid?  Age?  Names  of  stars?  25.  Stars,  how  further  distia 
pnished?  Single  Ftars?  Double,  Ac.?  Binary?  What  other  name?  Variable  stars. 
VVhHt  other  name  and  why?  New  stars?  Nebulous?  26.  What  are  clusters ?  Ncbu 
W?  Resolvable  Nebula?'?  Irresolvable ?  Annular?  Planetary? 


CLASSIFICATION    OF    STARS,    NEBULAE,    ETC.  17 

as-  ye-  been  thus  resolved.  Annular  Nebula  are  those  that  have 
the  form  of  an  annulus  or  ring.  Planetary  Nebula  are  those 
that  resemble  planets  in  form,  and  in  the  sharpness  of  their  out- 
line. Stellar  Nebula  are  those  with  a  star  in  the  centre,  the 
same  as  nebulous  stars,  already  described  (25). 

A  more  detailed  account  of  the  double  stars,  clusters  and  nebulae,  will  be  given  after 
the  student  has  become  somewhat  familiar  with  the  constellations. 

21.  We  may  now  imagine  the  pupil  roady  to  begin  the  study 
of  the  visible  heavens.  The  first  thing  of  importance  is  to  fix 
upon  the  proper  starting  point.  This,  on  many  accounts,  would 
seem  to  be  the  North  Polar  Star.  Its  position  is  apparently 
the  same  every  hour  of  the  night  throughout  the  year,  while  the 
other  stars  are  continually  moving.  Many  of  the  stars  also  in 
that  region  of  the  skies  never  set,  so  that  when  the  sky  is  clear, 
they  may  be  seen  at  any  hour  of  the  night.  They  revolve  about 
the  pole  in  small  circles,  and  never  disappear  below  the  horizon. 

On  this  account  they  are  said  to  be  within  the  circle  of  perpetual  apparition.  On  the 
other  hand,  the  identity  of  the  North  Polar  Star,  strange  as  it  may  appear,  is  not  so 
easily  determined  by  those  who  are  just  entering  upon  this  study,  as  that  of  some  others. 
For  this  reason,  the  point  directly  overhead,  called  the  zenith,  is  preferable,  since  upon 
this  point  every  one  can  fix  with  certainty  in  whatever  latitude  he  may  be.  It  will  be 
alike  to  all  the  central  point  of  the  visible  heavens,  and  to  it  the  pupil  will  learn  imper- 
ceptibly to  refer  the  bearing,  motion,  and  distances  of  tne  heavenly  bodies. 

That  meridional  point  in  each  map,  whose  declination  corresponds  with  the  latitude 
of  the  place  of  observation,  represents  the  zenith  of  the  heavens  at  that  place;  and 
th^se  constellations  of  stars  which  occupy  this  position  en  the  maps,  will  be  seen  directly 
overhead  at  9  o'clock  in  the  evening  of  the  day  through  which  the  meridian  passes. 
Thus  in  Georgia,  for  instance,  the  starting  point  should  be  those  stars  which  are  situated 
in  this  meridian  near  the  38d  degree  of  north  declination,  while  in  New  England  it 
should  be  those  which  are  situated  in  it  near  the  42d  degree. 

28.  We  might,  however,  begin  with  the  stars  near  either  of 
the  meridians  represented  on  the  maps,  the  only  rule  of  selection 
being  to  commence  at  that  which  approaches  nearest  to  being 
overhead  at  the  time  required.  We  have  chosen  for  our  starting 
point  in  this  work  that  meridian  which  passes  through  the  vernal 
er,uinox  at  the  first  point  of  Aries,  not  only  because  it  is  the 
meridian  from  which  the  distances  of  all  the  heavenly  bodies  are 
measured  ;  but  especially  because  the  student  will  thus  be 
enabled  to  observe  and  compare  th?  progressive  motion  of  the 
constellations  according  to  the  order  in  which  they  are  always 
arranged  in  catalogues,  and  also  to  mark  the  constellations  of 
the  Zodiac  passing  overhead  as  they  rise  one  after  another  in 
their  order,  and  to  trace  among  them  the  orbits  of  the  Earth 
and  of  the  other  planets. 

27.  What  first  important  in  commenc:*ig  study  of  the  heavens?  What  star  woulj 
seem  best  starting  point?  Why?  Wh>  not  the  best?  What  point  preferable,  an  1 
wliy?  Illustration  from  map.  28.  With  what  stars  might  we  begin?  What  raerid'un 
rhoseu  by  the  author?  Why* 


PART  I. 
THE    CONSTELLATIONS 


CHAPTER  I. 

CONSTELLATIONS   ON  THE  MERIDIAN  IN  NOVEMBER 

ANDROMEDA.— MAP  II.* 

29.  IF  we  look  directly  overhead  at  10  o'clock,  on  the  10th 
of  November,  we  shall  see  the  constellation  celebrated  in  fable 
by  the  name  of  ANDROMEDA.     It  is  represented  on  the  map  by  the 
figure  of  a  woman  having  her  arms  extended,  and  chained  by 
her  wrists  to  a  rock.     It  is  bounded  N.  by  Cassiopeia,  E.  by 
Perseus  and  the  head  of  Medusa,  and  S.  by  the  Triangles  and 
the  Northern  Fish.     It  is   situated  between  20°  and  50°  of  K. 
decimation.      Its  mean  right   ascension  is  nearly  15°;  or  one 
hour  E.  of  the  equinoctial  colure. 

30.  It  consists  of  66  visible  stars,  of  which  three  are  of  the2d 
magnitude,  and  two  of  the  3d  ;  most  of  the  rest  are  small.    The 
stars  directly  in  the  zenith  are  too  small  to  be  seen  in  the  pre- 
sence of  the  moon,  but  the  bright  star  Almaack  (y),  of  the  2d 
magnitude,  in  the  left  foot,  may  be  seen  13°  due  E.,  and  Merach 
((3),    of  the   same   magnitude,   in  the  girdle  7°    south  of  the 
zenith.     This  star  is  then  nearly  on  the  meridian,  and  with  two 
others  N.W.  of  it  forms  the  girdle. 

The  three  stars  forming  the  girdle  are  of  the  2d,  3d,  and  4th 
magnitude,  situated  in  a  row,  3°  and  4°  apart,  and  are  called 
Merach,  Mu,  and  Nu. 

31.  If  a  straight  line,  connecting  Almaack  with  Merach,  be 

*  As  the  eastward  motion  of  the  earth  in  her  orbit  causes  the  sun  to  pass  eastward 
annually  around  the  heavens,  and  the  constellations  to  rise  earlier  and  earlier  (19),  the 
student  will  find  it  necessary  to  proceed  eastward  around  the  heavens,  in  studying  the 
constellations.  And  as  the  right  hand  of  the  map  is  west,  and  the  left  hand  east,  we 
begin  with  the  equinoctial  colure,  map  II.,  and  proceed  to  the  left  in  the  order  in  which 
the  constellations  successively  arise. 


29.  What  constellation?     Maps,  and  why?  (Note.)     How  Andromeda,  represented? 
Boundaries?     Situation?     Right  ascension  and  declination?        8<>.  Number  of  stars 
Magnitude?     Almaack?     Merach?     "Girdle?"        31.  Situation  of  Delta  ?    Magnitude 
t£o\v  otherwise  known?   Alpheratz?    Substance  of  note  ^fine  prmt)? 


ANDROMEDA.  19 

produced  south  -westerly,  8°  farther,  it  will  reach  to  (8)  Ddta, 
a  star  of  the  3d  magnitude  in  the  left  breast.  This  star  may  be 
otherwise  known  by  its  forming  a  line,  N.  and  S.,  with  two 
smaller  ones  oil  either  side  of  it  ;  or,  by  its  constituting,  with 
two  others,  a  very  small  triangle,  S.  of  it. 

Nearly  in  a  line  with  Almaack,  Merach  and  Delta,  but  curv- 
ing a  little  to  the  N.  7°  farther,  is  a  lone  star  of  the  2d  magni- 
tude, in  the  head,  called  Alpheratz  (a).  This  is  the  N.E.  cor 
ner  of  the  great  "  Square  of  Pegasus,"  to  be  hereafter  described. 

It  will  be  well  to  have  the  position  of  Alpheratz  well  fixed  in  the  mind,  because  it  is 
but  one  minute  west  of  the  great  equinoctial  colure,  or  first  meridian  of  the  heavens, 
and  forms  nearly  a  right  line  with  Algenify  in  the  wing  of  Pegasus,  14°  d.  of  it,  and  with 
Beta  in  Cassiopeia,  30°  N.  of  it.  If  a  line,  connecting  these  three  stars,  be  produced,  it 
will  terminate  in  the  pole.  These  three  guides,  in  connection  with  the  North  Polar  Star, 
point  out  to  astronomers  the  position  of  that  great  circle  in  the  heavens  from  which  the 
right  ascension  of  all  the  heavenly  bodies  is  measured. 

MYTHOLOGICAL  HISTORY, 

82.  The  story  of  Andromeda,  from  which  this  constellation  derives  its  name,  is  as  follows: 
She  was  daughter  of  Cepheus,  King  of  Ethiopia,  by  Cassiopeia.  She  was  promised  in 
marriage  to  Phineus,  her  uncle,  when  Neptune  drowned  the  kingdom,  and  sent  a  sea 
monster  to  ravage  the  country,  to  appease  the  resentment  which  his  favorite  nymphs 
bore  against  Cassiopeia,  because  she  had  boasted  herself  fairer  than  Juno  and  the 
Nereides.  The  oracle  of  Jupiter  Ammon  was  consulted,  and  nothing  could  pacify  the 
anger  of  Neptune  unless  the  beautiful  Andromeda  should  be  exposed  to  the  sea  monster. 
She  was  accordingly  chained  to  a  rock  for  this  purpose,  near  Joppa  (now  Jaffa,  in  Syria), 
and  at  the  moment  the  monster  was  going  to  devour  her,  Perseus,  who  was  then  return- 
ing through  the  air  from  the  conquest  of  the  Gorgons,  saw  her,  and  was  captivated  by 
her  beauty. 

"Chained  to  a  rock  she  stood  ;  young  Perseus  stay'd 
His  rapid  flight,  to  woo  the  beauteous  maid." 

He  promised  to  deliver  her  and  destroy  the  monster  if  Cepheus  would  give  her  to 
him  in  marriage.  Cepheus  consented,  and  Perseus  instantly  changed  the  sea  monster 
into  a  rock,  by  showing  him  Medusa's  head,  which  was  still  reeking  in  his  hand.  The, 
enraged  Phineus  opposed  their  nuptials,  and  a  violent  battle  ensued,  in  which  he,  also, 
was  turned  into  a  stone,  by  the  petrifying  influence  of  the  Gorgon's  head. 

The  morals,  maxims,  and  historical  events  of  the  ancients,  were  usually  communicated 
in  fable  or  Allegory.  The  fable  of  Andromeda  and  the  sea  monster  might  mean  that  she 
was  courted  by  some  monster  of  a  sea-captain,  who  attempted  to  carry  her  away,  but 
was  prevented  by  another  more  gallant  and  successful  rival. 

TELESCOPIC  OBJECTS. 

33.  Under  the  head  of  Telescopic  Objects,  will  be  included  clusters  and  nebulae  that 
are  visible  to  the  naked  eye,  as  well  as  the  principal  objects  of  interest  that  are  strictly 
telescopic.  In  describing  the  location  of  these  objects,  R.  A.  will  denote  Right  Ascen- 
sion; and  Dec.,  Declination.  The  initials  N.  and  S.  will  indicate  whether  the 
declination  is  North  or  /South  of  the  equinoctial. 

In  describing  the  location  of  the  telescopic  object,  the  R.  A.  will  be  given  in  time, 
viz.,  in  hours,  minutes,  and  seconds,  instead  of  degrees,  minutes,  and  seconds:  each 
hour  answering  to  15°.  The  hour  circles  are  listinctly  drawn  on  all  tlie  maps,  the  first 
being  15°  east  of  the  equinoctial  colure  (Map  H.),  and  so  on  eastward  to  the  same  point 
again.  The  hours  will  be  seen  marked  just  under  the  equinoctial,  which  is  marked  oft 
into  degrees,  each  of  which  answers  to  four  minutes  of  time.  The  student  will  soon  find 
it  much  more  convenient  to  reckon  R.  A.  by  /tours,  on  the  maps,  than  by  degrees,  &c. 

32.  HISTORY  . — What  may  it  have  meant  ? 

33.  What  included  among  Telescopic  Objects?    What  meant  by  R.  A.?    Dec.?    N.  ana 
8.?     How  R.  A.  laid  down?     How  on  map?     What  mode  of  describing  components  of 
double  stars?     Of  a  Andromeda  ?     Of  discrepancies  between   R.  A.  given,  and   loca- 
tion  of   stars  on   the  maps?     How  is  R.  A.  {riven  in  locating  objects?     Why?      Ho* 
are  hours  marked  on  the  maps?     The  minutes? 


20  ASTRONOMY. 

84.  In  consequence  of  the  perpetual  recession  of  the  equinoxes  westward,  the  R.  A. 
of  objects  is  constantly  increased  by  about  50"  per  year.  It  is  vain,  therefore,  to  attempt 
tc  give  R.  A.  for  the  Ume  when  a  book  will  be  us^d;  or  to  construct  maps  that  will 
show  objects  in  their  true  place,  for  different  years  to  come.  The  necessary  allowance 
jmst  be  made  in  all  cases  ;  so  that  the  R.  A.  for  one  epoch  is  about  as  good  as  another. 
The  R.  A.  here  given  is  from  Smyth's  Celestial  Cycle,  epoch  Jan.  1,  1840.  Maps  should 
be  re-engraved  every  fifty  years,  but  for  all  shorter  periods  allowance  can  be  made  by 
the  student.  As  the  maps  accompanying  this  work  were  drawn  and  engraved  in. 1835, 
their  present  R.  A.  (1854)  is  about  17'  or  4m.  of  time  east  of  their  places  on  the  maps. 

35  The  order  in  which  the  telescopic  objects  will  be  arranged  is  first  the  double  stars  ; 
secondly,  clusters ;  and  lastly  the  nebulas.  The  double  stars  will  be  classed  according, 
to  their  order  in  the  respective  constellations;  i.e.,  a  first,  /?  next,  &c.  Thus,  as  the 
largest  objects  are  first  named,  the  student  can  begin  with  those  easiest  found,  a/id 
requiring  the  least  telescopic  power;  and  proceed  from  the  easier  to  those  more  diffi- 
cult. The  same  plan  is  generally  pursued  with  the  clusters  and  nebulae. 

TELESCOPIC    OBJECTS    IN    ANDROMEDA. 

1.  a  ANDROMEDA  (Alpheratz)— A  star  with  a  minute  companion,  R.  A.  Oh.  Om.  08s.. 
Pec.,  N.  28°  12'  05".   A.  1,  bright  white  ;  B.  11,  purplish.     On  the  map  it  is  west  of  the 
equinoctial,  the  map  having  been  engraved  some  twenty  years ;  but  the  equinox  having 
constantly  receded  westward,  had  passed  Alpheratz  before  1840,  some  8'.     Similar  dis- 
crepancies between  the  R.  A.  given  and  the  location  of  different  stars  on  the  map,  are 
due  to  the  same  cause. 

2.  ft  ANDROMEDA  (Merach) — A  bright  star  with  a  distant  telescopic  companion,  R.  A. 
Ih.  00m.  4Ts. ;  Dec.,  N.  34°  46'  08'.    A.  2,  fine  yellow ;  B.  12,  pale  blue,  with  several  small 
stars  in  the  field. 

3.  y  ANDROMEDA  (AlmuacK) — A  SPLENDID  DOUBLE  STAR  on  the  right  foot,  R.  A.  Ih.  54m. 
06s;  Dec.  N.  41°  33'  06".     A.  3}£,  orange  color  ;  B.  5J$,  emerald  green.     Found  by  a  line 
from  6  to  /3,  and  about  twice  as  far  beyond.     (Map  VIII.,  Pig.  1.) 

4.  fj  ANDROMEDA — A  bright  star  on  the  right  breast,  with  a  distant  telescopic  com- 
panion, R.  A.  Oh.  30m. 47s. ;  Dec.,  N.  29°  59'  01".    A.  3,  t range;  B.  llfc,  dusky  ;  with  the 
small  stars  in  the  southern  part  of  the  field. 

5.  K  ANDROMEDA — A  wide,  but  delicate  TRIPLE  STJR,  in  the  northern  hand ;  midway 
between  0  Pegasi  and  a.  Cassiopeia  ;  or  about  18°  from  each  ;  R.  A.  23h.  32m.  83s ;  Dec., 
N.  43°  27' 0".     A.  5,  brilliant  white;  B.  14,  dusky;  C.  12,  ash-colored. 

6.  AN  ELONGATED  NEBULA  on  the  lady's  right  foot.  R.  A,2h.  12m.  35s. ;  Dec.,  N.4J"  36". 
It  was  discovered  by  Miss  Caroline  Herschell,  in  1783.    Sir  William  Herschell  described 
it  as  having  "a  black  division  or  chink  in  the  middle."     He  regarded  it  as  a  flat  ring 
of  enormous  dimensions,  seen  very  obliquely.     Captain  Smyth  says:  "In  my  telescope 
it  is  certainly  brighter  at  the  edges  than  along  the  central  part."  See  map  VIII.,  Fig.  21. 

7.  About  2°  from  Nu  at  the  north-western  extremity  of  the  girdle,  R.  A.  00°  34m.  05s., 
N.  Dec.,  40°  23'  06",  is  n.  remarkable  nebula  of  very  minute  stars,  and  the  only  one  of 
the  kind  which  is  ever  visible  to  the  naked  eye.    'It  resembles  two  cones  of  light,  joined 
at  their  base,  about  %°  in  length,  and  \£°  in  breadth.     It  was  known  as  far  back  as  A.D. 
905,  is  of  an  oval  shape,  and  is  described  by  Smyth  as  "an  overpowering  nebula,  with 
a  companion  about  25'  in  the  south  vertical."     Sir  William  Herschell  considered  this  the 
nearest  of  all  the  great  nebulae,  and  yet  so  remote  thai  it  would  require  6,000  years  for 
light  to  pass  from  it  to  our  system,  though  flying  at  the  rate  of  190,000  miles  per  second  1 
Fig.  22,  map  VIII.,  is  a  representation  of  this  object. 

PISCES  (THE  FISHES).— MAP  Y. 

36.  This  constellation  is  now  the  first  in  order  of  the  twelve 
constellations  of  the  Zodiac,  and  is  usually  represented  by  two 
fishes  tied  a  considerable  distance  apart,  at  the  extremities  of  a  long 
undulating  cord,  or  ribbon.  It  occupies  a  large  triangular  space 

84.  What  said  of  tir  s  change  of  R.  A.  of  objects?  Cause?  Epoch  of  R.  A.  given  iu 
book?  Of  that  marked  on  maps?  Allowance  to  be  made  in  finding  objects  by  maps 
&5.  Order  in  which  objects  are  presented  ?  Advantage  of  this  arrangement? 

TELESCOPIC  OBJECTS.— What  double  stars?    a?    /3?     >?    What  clusters   T  nebului 
yi,(7wn   on  map,  or  not? 

?-«.  Pisces?    Where  situated?    What  now  callel9 


PISCES.  i>l 

m  the  heavens,  and  its  outline  at  first  is  somewhat  difficult  to  be 
traced. 

In  consequence  of  the  annual  precession  of  the  stars,  the  constellation  Pisces  has  now 
oome  to  occupy  the  sign  Aries ;  each  constellation  having  advanced  one  whole  sign  in 
the  order  of  the  Zodiac.  The  Sun  enters  the  sign  Pisces,  while  the  Earth  enters  that  of 
Virgo,  about  the  19th  of  February,  but  he  does  not  reach  the  constellaUon  Pisces  before 
the  6th  of  March.  The  Fishes,  therefore,  are  now  called  the  "  Leaders  of  the  Celestial 
Hosts." — See  Aries. 

3t.  That  loose  assemblage  of  small  stars  directly  south  of 
Merach,  in  the  constellation  of  Andromeda,  constitutes  the 
Northern  Fish,  whose  mean  length  is  about  16°,  and  breadth, 
7°.  Its  mean  right  ascension  is  15°,  and  its  declination  25°  N. 
Consequently,  it  is  on  the  meridian  the  24th  of  November  ;  and 
from  its  breadth,  is  more  than  a  week  in  passing  over  it. 

38.  The  Northern  Fish  and  its  ribbon,  beginning  at  Merach, 
may  by  a  train  of  small  stars,  be  traced  in  a  S.  S.  easterly  direc- 
tion, for  a  distance  of  33°,  until  we  come  to  the  star  El  liischa, 
of  the  3d  magnitude,  which  is  situated  in  the  node,  OT  flexure  of 
the  ribbon.     This  is  the  principal  star  in  the  constellation,  and 
is  situated  2°  N.  of  the  equinoctial,  and  53  minutes  east  of  the 
meridian. 

Seven  degrees  S.  E.  of  El  Rischa,  passing  by  three  cr  four  very  small  stars,  we  come  to 
Mira,  in  the  whale,  a  star  of  about  the  8d  magnitude,  and  known  as  the  "  Wonderful 
Star  of  1596."  El  Rischa  may  be  otherwise  identified  by  means  of  a  remarkable  cluster 
of  five  stars  in  the  form  of  a  pentagon,  about  15°  E.  of  it. — See  Cetus. 

39.  From  El  Rischa  the  ribbon  or  cord  makes  a  sudden 
flexure,  doubling  back  across  the  ecliptic,  where  we  meet  with 
three  stars  of  the  fourth  magnitude  situated  in  a  row  3  and  4° 
apart,  marked  on  the  map  Zeta,  Epsilon,-. Delta.     From  Delta 
the  ribbon  runs  north  and  westerly  along  the  Zodiac,  and  termi- 
nates at  Beta,  a  star  of  the  4th  magnitude,  11°  S.  of  Markab 
hi  Pegasus. 

This  part  of  the  ribbon,  including  the  Western  Fish  at  the  end  of  it,  has  a  mean 
declination  of  5°  N.,  and  may  be  seen  throughout  the  month  of  November,  passing  the 
meridian  slowly  to  the  W.,  near  where  the  sun  passes  it  on  the  1st  of  April. 

40.  Twelve  degrees  W.  of  this  Fish,  there  are  four  small  stars 
situated  in  the  form  of  the  letter  Y.     The  two  Fishes,  and  the 
cord  between  them,  make  two  sides  of  a  large  triangle,  30°  and 
40°  in  length,  the  open  part  of  which  is  towards  the  N.  W 
When  the  Northern  Fish  is  on  the  meridian,  the  Western  is 
nearly  two  hours  past  it.     This  constellation  is  bounded  N.  by 

87.  Northern  Fish?  Length?  Dec.?  When  on  the  meridian  ?  88.  How  trace  thu 
Northern  Fish?  To  what  star?  Magnitude?  Where  situated?  89.  From  El  Rischa f 
From  Delta?  Mean  declination  of  this  part  of  the  ribbon?  40.  What  12'  west  of 
this  fish?  ^aat  do  the  two  fishos,  &c.,  make?  Boundaries  of  Pisces? 


22  ASTRONOMY. 

Andromeda,  W.  by  Andromeda  and  Pegasus,  S.  by  the  Cascade, 
and  E.  by  the  Whale,  the  Ram  and  the  Triangles. 

When,  to  enable  the  pupil  to  find  any  star,  its  direction  from  another  is  given,  the 
latter  is  always  understood  to  be  on  the  meridian. 

After  a  little  experience  with  the  maps,  even  though  unaccompanied  by  directions, 
th,j  ingenious  youth  will  be  able,  of  himself,  t«  devise  a  great  many  expedients  and  facili 
ties  for  tracing  the  constellations,  or  selecting  out  particular  stars. 

In  using  a  circumpolar  map,  face  the  pole,  and  hold  it  up  in  your  hands  in  such  a 
manner  that  the  part  which  contains  the  name  of  the  given  month  shall  be  uppermos\ 
and  you  will  have  a  portraiture  of  the  heavens  as  seen  at  that  time. 

The  constellations  about  the  Antarctic  Pole  are  not  visible  in  the  United  States  ; 
those  about  the  Arctic  or  Northern  Pole,  are  always  visible. 

HISTORY. 

41.  The  ancient  Greeks,  who  have  some  fable  to  account  for  the  origin  of  almos 
every  constellation,  say,  that  as  Venus  and  her  son  Cupid  were  onevday  on  the  banks  ot 
the  Euphrates,  they  were  greatly  alarmed  at  the  appearance  of  a  terrible  giant,  named 
Typhon.  Throwing  themselves  into  the  river,  they  were  changed  into  fishes,  and  by 
this  means  escaped  danger.  To  commemorate  this  event,  Minerva  placed  two  fishes 
among  the  stars. 

According  to  Ovid,  Homer,  and  Virgil,  this  Typhon  was  a  famous  giant.  He  had  a  hun- 
dred heads,  like  those  of  a  serpent  or  dragon.  Flames  of  devouring  fire  daa-ted  from  his 
mouth  and  eyes.  He  was  no  sooner  born,  than  he  made  war  against  heaven,  and  so 
frightened  the  gods,  that  they  fled  and  assumed  different  shapes.  Jupiter  became  a 
ram :  Mercury,  an  Ibis ;  Apollo,  a  crow;  Juno,  a  cow;  Bacchus,  a  goat;  Pi».na,  a  cat; 
Venus,  a  fish,  Ac.  The  father  of  the  gods,  at  last,  put  Typhon  to  flight,  and  crushed  him 
under  Mount  /Etna. 

The  sentiment  implied  in  the  fable  of  this  hideous  monster,  is  evidently  this :  that 
there  is  in  the  world  a  description  of  men  whose  mouth  is  so  "  full  of  cursing  and  bitter- 
ness," derison  and  violence,  that  modest  virtue  is  sometimes  forced  to  disguise  itself, 
or  flee  from  their  presence. 

In  the  Hebrew  Zodiac,  Pisces  is  allotted  to  the  escutcheon  of  Simeon. 

No  sign  appears  to  have  been  considered  of  more  malignant  influence  than  PusMJ. 
The  astrological  calendar  describes  the  emblems  of  this  constellation  as  indicative  of 
violence  and  death.  Both  the  Syrians  and  Egyptians  abstained  from  eating  fish, 
out  of  dread  and  abhorrence ;  and  when  the  latter  would  represent  anything  as  odious, 
or  express  hatred  by  hieroglyphics,  they  painted  a/w>7t. 

TELESCOPIC    OBJECTS. 

1.  a  PISCICM  (El  Jfischa) — A  close  double  star  in  the  eastern  extremity  of  the  ribbon, 
R.  A.  Ih.  53m.  46s. ;  Dec.  N.  1°  59'  03'.    A.  5,  pale  green ;  B.  6,  blue ;  a  splendid  object, 
and  easily  found. 

2.  £  PISCIUM — A  neat  double  star  in  the  ribbon,  about  13°  north-west  of  a,  R.  A.  Ih. 
5m.  21  s.  ;  Dec.  N.  6°  43'  07".     A.  6,  silvery  white ;  B.  8,  pale  gray ;  a  fine  object. 

3.  0  PisciUM-»A  close  double  star  in  the  space  between  the  two  fishes,  about  half-way 
between  7j  Andromeda   and   (j  Ceti;  R.  A.  Ih.  2m.  31s. ;  Dec.  N.  8°  42'.    A.  8,  white; 
B.  14,  pale  blue. 

4.  A  neat  DOUBLE  STAR,  about  4°  south  of  Algenib,  in  the  wing  of  Pegasus,  R.  A.  Oh- 
1m.  53s. ;  Dec.  N.  10°  14'  06".    A.  6,  silvery  white ;  B.  13J$,  pale  blue. 

5.  A  FAINT  NEBULA  in  the  eye  of  the  western  Fish,  about  10°  south-half-east  of  Mar- 
*ub,  near  y  Piscium;  R.  A.  23h.  06m.  86s. ;  Dec.  8°  89'  7" :  a  very  difficult  object. 

CASSIOPEIA.— MAP  VI. 

42.  Cassiopeia  is  represented  on  the  celestial  map  in  regal  state, 
seated  on  a  throne  or  chair,  holding  in  her  left  hand  the  brand) 

41.  HISTORY? — Greek  account?  Ovid's  and  others?  Sentiment  or  moral?  Hebre-r 
Zodiac?  Astrology? 

TELESCOPIC  OBJECTS. — Double  stars       Clusters?    Nebulas?    Shown  on  map,  or  not? 
4i.  Cassiopeia  ?     How  represented       Head? 


CASSIOPEIA.  <J3 

of  a  palm  tree.  Her  head  and  body  are  seen  in  the  Milky  Way. 
H  2r  foot  rests  upon  the  Arctic  Circle,  upon  which  her  chair  is. 
placed  She  is  surrounded  by  the  chief  personages  of  her  royal 
family.  The  king,  her  husband,  is  on  her  right  hand — Perseus, 
her  son-in-law,  on  her  left—  and  Andromeda,  her  daughter,  just 
above  her. 

43.  This  constellation  is  situated  26°  N.  of  Andromeda,  and 
midway  between  it  and  the  North  Polar  Star.     It  may  be  seen 
from  our  latitude,  at  all  hours  of  the  night,  and  may  be  traced 
out  at  almost  any  season  of  the  year.     Its  mean  declination  is 
60P  N.  and  its  right  ascension  12°.     It  is  on  our  meridian  the 
22d  of  November,  but  does  not  sensibly  change  its  position  for 
several  days  ;  for  it  should  be  remembered  that  the  apparem 
motion  of  the  stars  becomes  slower  and  slower,  as  they  approxi- 
mate the  poles. 

44.  Cassiopeia  is  a  beautiful  constellation,  containing  55  stars 
that  are  visible  to  the  naked  eye  ;  of  which  four  are  of  the  3d 
magnitude,  and  so  situated  as  to  form,  with  one  or  two  smaller 
ones,  the  figure  of  an  inverted  chair. 

"  Wide  ner  stars 

Dispersed,  nor  shine  with  mutual  aid  improved ; 
Nor  dazzle,  brilliant  with  contiguous  Same : 
Their  number  fifty-five." 

45.  Caph,  in  the  garland  of  the  chair,  is  almost  exactly  in  the 
equinoctial  colure,  30°    N.of  Alpheratz,  with  which,  and  the 
Polar  Star,  it  forms  a  straight  line.     Caph  is  therefore  on  the 
meridian  the  10th  of  November,  and  one  hour  past  it  on  the 
24th.     It  is  the  westernmost  star  of  the  bright  cluster.     Shedir, 
in  the  breast,  is  the  uppermost  star  of  the  five  bright  ones,  and 
is  5°  S.  E.  of  Caph  :  the  other  three  bright  ones,  forming  the 
chair,  are  easily  distinguished,  as  they  meet  the  eye  at  the  first 
glance. 

There  is  an  importance  attached  to  the  position  of  Caph  that 
concerns  the  mariner  aad  the  surveyor.  It  is  used,  in  connec- 
tion with  observations  on  the  Polar  Star,  for  determining  the 
latitude  of  places,  and  for  discovering  the  magnetic  variation  of 
the  needle. 

46.  It  is  generally  supposed  that  the  North  Polar  Star,  so 
called,  is  the  real  immovable  pole  of  the  heavens  :  but  this  is  a 
mistake.     It  is  so  near  the  true  pole  that  it  has  obtained  the 

43.  Situation?  How  seen?  R.  A. .and  Dec.?  When  on  meridian?  44.  Number  of 
stars?  Magnitudes?  Figure?  Character  of  this  constellation?  45.  Caph?  How 
situated?  When  on  merid'an?  Shedir?  Importance  attached  to  Caph?  46.  Pole 
Btar?  Is  it  the  tn: e  pole?  What  variation?  Uow  pole  star  situated  with  reference  to 


JJ4  ASTRONOMY, 

appellation  of  the  North  Polar  Star  ;  but  it  is,  in  reality,  more 
than  a  degree  and  a  half  distant  from  it,  and  revolves  about  the 
true  pole  every  24  hours,  in  a  circle  whose  radius  is  1°  31'.  It 
will  consequently,  in  24  hours,  be  twice  on  the  meridian,  once 
above,  and  once  below  the  pole  ;  and  twice  at  its  greatest  elonga- 
tion E.  and  W. 

The  Polar  Star  not  being  exactly  in  the  N.  pole  of  the  heavens,  but  one  degree  and 
81  minutes  on  that  side  of  it  which  is  towards  Caph,  the  position  of  the  latter  becomes 
important,  as  it  always  shows  on  which  side  of  the  true  pole  the  polar  star  is. 

There  is  another  important  fact  in  relation  to  the  position  of  this  star.  It  is  equidis- 
tant froia  the  pole,  and  exactly  opposite  another  remarkable  star  in  the  square  of  the 
Great  Bear,  on  the  other  side  of  the  pole.  [See  Megres.]  It  also  serves  to  mark  a  spot 
in  the  starry  heavens,  rendered  memorable  as  being  the  place  of  a  lost  star.  Two  hun- 
dred and  fifty  years  ago,  a  bright  star  shone  6°  N.  N.  E.  of  Caph,  where  now  is  a 
dark  void ! 

On  the  8th  of  November,  15T2,  Tycho  Brahe  and  Cornelius  Gemma  saw  a  star  in  the 
constellation  of  Cassiopeia,  which  became,  all  at  once,  so  brilliant,  that  it  surpassed  the 
splendor  of  the  brightest  planets,  and  might  be  seen  even  at  noonday.  Gradually, 
this  great  brilliancy  diminished,  until  tho  15th  of  March,  1573,  when,  without  moving 
from  its  place,  it  became  utterly  extinct. 

Its  color,  during  this  time,  exhibited  all  the  phenomena  of  a  prodigious  flame — first, 
it  was  of  a  dazzling  white,  then  of  a  reddish  yellow,  and  lastly  of  an  ashy  paleness,  in 
which  its  light  expired.  It  is  impossible,  says  Mrs.  Somerville,  to  imagine  anything 
more  tremendous  than  a  conflagration  that  could  be  visible  at  such  a  distance.  It  was 
seen  for  sixteen  months.  Some  astronomers  imagined  that  it  would  reappear  again 
after  150  years  ;  but  it  has  never  been  discovered  since.  This  phenomenon  alarmed  all 
the  astronomers  of  the  age,  who  beheld  it ;  and  many  of  them  wrote  dissertations  con- 
cerning it. 

Rev.  Professor  Vince,  one  of  the  most  learned  and  pious  astronomers  of  the  age,  has 
this  remark : — "  The  disappearance  of  some  stars  may  be  the  destruction  of  that  system 
at  the  time  appointed  by  the  Deity  for  the  probation  of  its  inhabitants ;  and  the  appear- 
ance of  new  stars  may  be  the  formation  of  new  systems  for  new  races  of  beings  then 
called  into  existence  to  adore  the  works  of  their  Creator." 

Thus,  we  may  conceive  the  Deity  to  have  been  employed  from  all  eternity,  and  thus 
he  may  continue  to  be  employed  for  endless  ages ;  forming  new  systems  of  beings  to 
adore  him;  and  transplanting  beings  already  formed  into  happier  regions,  who  will  con- 
tinue to  rise  higher  and  higher  in  their  enjoyments,  and  go  on  to  contemplate  system 
after  system  through  th<;  boundless  universe. 

LA  PLACE  says : — As  to  those  stars  which  suddenly  shine  forth  with  a  very  vivid  light, 
and  then  immediately  disappear,  it  is  extremely  probable  that  great  conflagrations,  pro- 
duced by  extraordinary  causes,  take  place  on  their  surface.  This  conjecture,  continues 
he,  is  confirmed  by  their  change  of  color,  which  is  analogous  to  that  presented  to  us  on 
the  earth  by  those  bodies  which  are  set  on  fire,  and  then  gradually  extinguished. 

The  late  eminent  Dr.  Good  also  observes  that — Worlds,  and  systems  of  worlds,  are  cot 
only  perpetually  creating,  but  also  perpetually  disapoearing.  It  is  an  extraordinary  fact, 
that  within  the  period  of  the  last  century,  not  less  than  thirteen  stars,  in  different  con- 
stellations, seem  to  have  totally  perished,  and  ten  new  ones  to  have  been  created.  In 
many  instances  it  is  unquestionable,  that  the  stars  themselves,  the  supposed  habitation 
of  other  kinds  or  orders  of  intelligent  beings,  together  with  the  different  plant ts  l>y 
which  it  is  probable  they  were  surrounded,  have  utterly  vanished,  and  the  spots  which 
they  occupied  in  the  heavens  have  become  blanks  !  What  has  befallen  other  systems  will 
assuredly  befall  our  own.  Of  the  time  and  the  manner  we  know  nothing,  but  the  fact  is 
incontrovertible ;  it  is  foretold  by  revelation ;  it  is  inscribed  in  the  heavens ;  it  is  feit 
through  the  earth.  Such  is  the  awful  and  daily  text ;  what  then  ought  to  be  the  comment? 

The  great  and  good  Beza,  falling  in  with  the  superstition  of  his  age,  attempted  to  prove 
that  this  was  a  comet,  or  the  same  luminous  appearance  which  conducted  the  magi,  or 
wise  men  of  the  East,  into  Palestine,  at  the  birth  of  our  Saviour,  and  that  it  now  appeared 
to  announce  his  second  coining. 

Caph  ?  What  other  important  fact  in  relation  to  the  position  of  Caph  ?  What  remark- 
able fact  stated?  By  whom  attested?  Describe  phenomenon?  Mrs.  fcoinervtlle'e 
remark?  Other  astronomers'?  Professor  Vince's  remarks?  The  author's?  La 
Place's?  Dr.  Good's?  Beza's? 


CEPHET7S.  ^ 

HISTORY. 

Cassiopeia  was  the  wife  of  Cepheus,  King  of  Ethiopia,  and  mother  of  Andromeaa.  She 
was  a  queen  of  matchless  beauty,  and  seemed  to  be  sensible  of  it ;  for  she  even  boasted 
herself  fairer  than  Juno,  the  sister  of  Jupiter,  or  the  Nereides — a  name  given  to  the  sea- 
nymphs.  This  so  provoked  the  ladies  of  the  sea,  that  they  complained  to  Neptune  of  the 
insult,  who  sent  a  frightful  monster  to  ravage  her  coast,  as  a  punishment  for  her  inso- 
lence. But  the  anger  of  Neptune  and  the  jealousy  of  the  nymphs  were  not  thus  appeased 
They  demanded,  and  it  was  finally  ordained  that  Cassiopeia  should  chain  her  daughter 
Andromeda,  whom  she  tenderly  loved,  to  a  desert  rock  on  the  beach,  and  leave  her 
exposed  to  the  fury  of  this  monster.  She  was  thus  left,  and  the  monster  »  proached , 
but  just  as  he  was  going  to  devour  her,  Perseus  killed  him. 
"The  saviour  youth  the  royal  pair  confess. 
And  with  heav'd  hands,  their  daughter's  bridegroom  bless." 

JEusden's  Ovid. 

TELESCOPIC    OBJECTS. 

1.  a  CASSIOPE.B (Shedir) — A  bright  star,  with  a  companion  in  the  bosom  of  the  figure; 
R.  A  Oh.  31m  29s.;  Dec.  65°  89' 05".    A  3,  pale  rose  tint;  B  10j£,  small  blue.     S-i/th 
and  Herschell  note  Shedir  as  variable. 

2.  ll  CAS8ioPE.fi  (Caph)—A  bright  star  on  the  left  side,  with  a  minute  companion  ; 
R.  A.  Oh.  Om.  42s.;  Dec.  N.  58"  16'  03".    A  2Jj,  whitish;  B  11^,  dusky.    Look  directly 
opposite  Negris,  in  the  great  dipper,  through  the  pole  star,  and  about  as  far  beyond. 

3.  y  CASSIOPE.K — A  bright  star  with  a  distant  companion  on  the  right  side  of  the  figure  ; 
R.  A.  Oh.  47m.  05s. ;  Dec.  N.  59°  50'  OS".    A  3,  brilliant  white;  B  13,  blue.    Mar,/  small 
»tars  in  the  field. 

4.  77  CASSIOPE^B — A  BINARY  STAR,  about  4°  from  a  towards  Polaris ;  R.  A.  Oh.  39m.  27s. , 
Dec.  N.  56°  57'  09".    A.  4,  pale  white ;  B.  7J*S,  purple.    Estimated  period  700  yeaid. 

5.  fi  CASSIOPE^B — A  coarse  TRIPLE  STAR  in  the  right  elbow ;    R.  A.  Oh.  57m.  23s  ;  Dec.  N. 
54°  OS'  01".    A  5}$,  deep  yellow ;  B  14,  pale  blue ;  C  11,  bluish.    Several  small  slars  in  the 
field. 

6.  <7   CASSIOPK^ — A  beautiful  double  star  in  the  left  elbow ;  R.  A.  23H.  50m.  55s. ;  Dec. 
N.  54°  51'  OS".     A  6,  flushed  white ;  B  8,  smalt  blue ;  the  colors  clear  and  distinct. 

7.  A  coarse  QUADRUPLE  STAR,  just  south  of  Cepheus'  right  hand;  or  about  27°  south- 
south-west  of  Polaris,  on  a  line  drawn  over  y  Cepliei.     R.  A.  23h.  17m.  45s. ;  Dec.  N.  64' 
24'  03".    A  5,  pale  yellow ;  B  9,  yellowish  ;  C  1 1,  and  D,  13,  both  blue. 

8.  A  LARGE  AND  STRAGGLING  CLUSTER,  between  the  footstool  of  Cassiopeia  and  the  head  of 
Cepheus;  R.  A.  Oh.  ISm.  10s.;  Dec.  N.  70°  30'  08".     A  line  from  y  Cassiopeze,  %  the  did 
tance  to  y  Cephei,  will  fall  upon  this  object.     A  coarse  double  star  in  the  field. 

9.  A  RICH,  BUT  SOMEWHAT  STRAGGLING  CLUSTER;  R.  A.  Oh.  24m.  5s. ;  Dec.  N.  62°  23'  09". 

Vicinity  splendidly  strewed  with   stars — a  double  star  in  the  centre.    Look  near  the 

star  /tr- 
lO.  A  LOOSE  CLUSTER,  including  a  small  double  star;  R.  A.  Oh.  34m.  15s.;  Dec.  N.  60* 

54' 07".    A  8 %,  B  11,  both  pale.    Situated  just  half  way  between  y  and  K. 

11.  A  LOOSE  CLUSTER  of  small  stars ;  R.  A.  Oh.  5Sm.  19s. ;  Dec.  N.  60"  44'.    On  a  line  from 
y  towards  f,  about  J4  the  distance. 

12.  A  CLUSTER  and  neat  double  star  on  a  line  from  a  through  <J,  and  about  2J$*  beyond. 
In  an  elegant  field  of  large  and  small  stars. 

18.  A  FINE  GALAXY  CLUSTER  of  minute  stars,  about  3*  south-west  of  /?,  and  about  the 
aame  distance  west  of  a.  R.  A.  23h.  49m.  07s. :  Dec.  N.  55°  49'  06".  A  glorious  assem- 
blage, both  in  extent  and  richness.  Resembles  a  crab,  having  spangled  rays  of  start?, 
spreading  over  many  fields  =  Map  VIII.,  Fig.  23. 


CEPHEUS.— MAP  VI. 

47.  Cepheus  is  represented  on  the  map  as  a  king,  in  his  royr.1 
robe,  with  a  sceptre  in  his  left  hand,  and  a  orown  of  stars  upcu 

H«JTOHY? — Who  was  Cassiopeia?  Personal  appearance?   Sad  consequences ?  Reacm  V 
TFLK«COPIC  OBJECT*  —Double  and  multiple  stars  ?     Clusters  ?    What  shown  oil  map  ? 
47.  How  is  Cepheus  represented?     Where  sjtuated? 


26  ASTRONOMY. 

his  head.  He  stands  in  a  commanding  posture,  with  his  left 
foot  over  the  pole,  and  his  sceptre  extended  towards  Cassiopeia, 
as  if  for  favor  and  defence  of  the  queen. 

"  Cepheus  illumes 

The  neighboring  heavens ;  still  faithful  to  his  queen, 
With  thirty-five  faint  luminaries  mark'd." 

This  constellation  is  about  25*  N.  W.  of  Cassiopeia,  near  the  2d  coil  of  Draco,  and  is  on 
the  meridian  at  8  o'clock  the  3d  of  November ;  but  it  will  linger  near  it  for  many  days. 
Like  Cassiopeia,  it  may  be  seen  at  aJ  hours  of  the  night,  when  the  sky  is  clear,  for  to  us  it 
never  sets. 

By  reference  to  the  lines  on  the  map,  which  all  meet  in  the  pole,  it  will  be  evident  that 
a  star,  near  the  pole,  moves  over  a  much  less  space  in  one  hour,  than  one  at  the  equi- 
noctial; and  generally,  the  nearer  the  pole,  the  narrower  the  space,  and  the  slower 
the  motion. 

The  stars  that  are  so  near  the  pole  may  be  better  described  by  their  polar  distance, 
than  by  their  declination.  By  polar  distance  is  meant,  the  distance  from  the  pole,  anJ 
u  what  the  declination  wants  of  90". 

48.  In  this  constellation  there  are  35  stars  visible  to  the 
naked  eye  ;  of  these,  there  glitters  on  the  left  shoulder,  a  star 
of  the  3d  magnitude,  called  Alderamin,  which  with  two  others  of 
the  same  brightness,  8°  and  12°  apart,  form  a  slightly  curved 
line  towards  the  N.  E.     The  last,  whose  letter  name  is  Gamma, 
is  in  the  right  knee,  19°  N.  of  Caph,  in  Cassiopeia.     The  middle 
one  in  the  line  is  Alphirk,  in  the  girdle.     This  star  is  one-third 
of  the  distance  from  Alderamin  to  the  pole,  and  nearly  in  the 
same  right  line. 

It  cannot  be  too  well  understood  that  the  bearings,  or  direction  of  one  star  from 
another,  as  given  in  this  treatise,  are  strictly  applicable  only  when  the  latter  one  is  on, 
or  near  the  meridian.  The  bearings  given,  in  many  cases,  are  not  the  least  approxima- 
tions to  what  appears  to  be  their  relative  position ;  and  in  some,  if  relied  upon,  will  lead 
to  errors.  For  example : — It  is  said  in  the  preceding  paragraph,  that  Gamma,  in  Cepheus, 
bears  19°  N.  of  Caph  in  Cassiopeia.  This  is  true,  when  Caph  is  on  the  meridian,  but  at 
this  very  moment,  while  the  author  is  writing  this  line,  Gamma  appears  to  be  19°  due 
west  of  Caph;  and  six  months  hence,  will  appear  to  be  the  same  distance  east  of  it. 
The  reason  is  obvious ;  the  circle  which  Cepheus  appears  to  describe  about  the  pole,  is 
within  that  of  Cassiopeia,  and  consequently  when  on  the  east  side  of  the  pole,  will  be 
within,  or  beticeen  Cassiopeia  and  the  pole— that  is,  west  of  Cassiopeia.  And  for  the 
same  reason,  when  Cepheus  is  on  the  west  side  of  the  pole,  it  is  between  that  and  Cassio- 
peia, or  east  of  it. 

Let  it  also  be  remembered,  that  in  speaking  of  the  pole,  which  we  shall  have  frequent 
occasion  to  do,  in  the  course  of  this  work,  the  North  Polar  Star  or  any  imaginary  point 
very  near  it,  is  always  meant ;  and  not,  as  some  will  vaguely  apprehend,  a  point  in  thg 
horizon,  directly  N.  of  us.  The  true  pole  of  the  heavens  is  always  elevated  just  as  many 
degrees  above  our  horizon,  as  we  are  north  of  the  Equator.  If  we  live  in  42°  N.  latitude, 
the  N.  pole  will  be  42°  above  our  horizon.  (See  North  Polar  Star.) 

49.  There  are  also  two  smaller  stars  about  9°  E.  of  Aldera- 
,mn  and  Alphirk,  with  which  they  form  a  square  ;  Alderamin 
being  the  upper,  and  Alphirk  the  lower  one  on  the  W.  8°  apart. 
In  the  centre  of  this  square  there  is  a  bright  dot,  or  semi-visible 
star. 

The  head  of  Cepheus  is  in  the  Milky-Way,  and  may  be  known 

48.  Number  of  stars  visible?  Principal  stars?  Situation?  49.  What  other  stars, 
and  situation  ?  Situation  of  the  food,  and  how  known  ?  Distance  of  this  Asterism  from 
the  pole  star  ? 


CEPHEUS.  2? 

*»v  three  stars  of  the  4th  magnitude  in  the  crown,  which  form  a 
small  acute  triangle,  about  9°  to  the  right  of  Alderamin.  The 
mean  polar  distance  of  the  constellation  is  25°,  while  that  of 
Alderamin  is  28°  10'.  The  right  ascension  of  the  forme"  is 
338°  ;  consequently,  it  is  22°  E.  of  the  equinoctial  colure. 

The  student  will  understand  that  right  ascension  is  reckoned  on  the  equinoctial,  froai 
the  first  point  of  Aries,  E.,  quite  round  to  the  same  point  again,  which  is  360°.  Now, 
88S*  measured  from  the  same  point,  will  reach  the  same  point  again,  within  22° ;  which  is 
the  difference  between  360°  and  33S*.  This  rule  will  apply  to  any  other  case. 

HISTORY. 

This  constellation  immortalizes  the  name  of  the  king  of  Ethiopia.  The  name  of  his 
queen  was  Cassiopeia.  They  were  the  parents  of  Andromeda,  who  was  betrothed  to 
Perseus.  Cepheus  was  one  of  the  Argonauts  who  accompanied  Jason  on  his  perilous 
expedition  in  quest  of  the  golden  fleece.  Newton  supposes  that  it  was  owing  to  thia 
circumstance  that  he  was  placed  in  the  heavens ;  and  that  not  only  this,  but  all  the 
ancient  constellations,  relate  to  the  Argonautic  expedition,  or  to  persons  some  way  con- 
nected with  it.  Thus,  he  observes,  that  as  Musseus,  one  of  the  Argonauts,  was  the  first 
Greek  who  made  a  celestial  sphere,  he  would  naturally  delineate  on  it  thos*1  figures  which 
had  some  reference  to  the  expedition.  Accordingly,  we  have  on  our  globes  to  this  day, 
the  Golden  Ram,  the  ensign  of  the  ship  in  which  Phryxus  fled  to  Colchis,  the  scene  o  ' 
the  Argonautic  achievements.  We  have  also  the  Bull  with  brazen  hoofs,  tamed  by 
Jason ;  the  Twins,  Castor  and  Pollux,  two  sailors,  with  their  mother  Leda,  in  the  foriii 
of  a.  Swan,  and  Argo,  the  ship  itself;  the  watchful  Dragon,  Hydra,  with  the  Cup  of 
Medea,  and  a  raven  upon  its  carcase,  as  an  emolem  of  death ;  also  Chiron,  the  Mastei 
of  Jason,  with  his  Altar  and  Sacrifice;  Hercules,  the  Argonaut,  with  his  club,  his  dart. 
and  vulture,  with  the  dragon,  crab,  and  lion  which  he  slew ;  and  Orpheus,  one  of  the 
company,  with  his  harp.  Ail  these,  says  Newton,  refer  to  the  Argonauts. 

Again;  we  have  Orion,  the  son  of  Neptune,  or,  as  some  say,  the  grandson  of  Minos, 
with  his  dogs,  and  hare,  and  river,  and  scorpion.  We  have  the  story  of  Perseus  in  the 
constellation  of  that  name,  as  well  as  in  Cassiopeia,  Cepheus,  Andromeda,  and  Cetus  • 
that  of  Calisto  and  her  son  Areas,  in  Ursa,  Major;  that  of  Icarius,  and  his  daughter 
Erigone,  in  Bootes  and  Virgo.  Ursa  Minor  relates  to  one  of  the  nurses  of  Jupiter 
Auriga,  to  Erichtonius  ;  OpMuchus,  to  Phorbas  ;  Sagittarius,  to  Crolus,  the  son  of  om 
of  the  Muses;  Capricorn,  to  Pan,  and  Aquarian  to  Ganymede.  We  have  also  Ariadne'* 
crown,  Bellerophon's  horse,  Neptune's  dolphin,  Ganymede's  eagle,  Jupiter's  goat,  with 
her  kids,  the  asses  of  Bacchus,  th«  fixhes  of  Venus  and  Cupid,  with  their  parent,  the 
southern  fish.  These,  according  to  Deltoton,  comprise  the  Grecian  constellations  men 
tioned  by  the  poet  Aratus;  and  all  relate,  as  Newton  supposes,  remotely  or  immediately 
to  the  Argonauts. 

It  may  be  remarked,  however,  that  while  none  of  these  figures  refer  to  any  transaction? 
of  a  later  date  than  the  Argonautic  expedition,  yet  the  great  disagreement  which  appears 
in  the  mythological  account  of  them,  proves  that  their  invention  must  have  been  o 
greater  antiquity  than  that  event,  and  that  these  constellations  were  received  for  some 
time  among  the  Greeks,  before  their  poets  referred  to  them  in  describing  the  particular  s 
of  that  memorable  expedition. 

TELESCOPIC  OBJECTS. 

1.  a  CRPHET  (Alderamin)-  A  FINK  STAR,  with  a  distant  companion  on  the  left  shoulder 
of  Cepheus;  R.  A.,  21h.  15m. ;  Dec.,  61*  54'.     It  is  about  half  way  between  Polaris  ami 
Deneb,  and  8°  south-west  from  ft  Cephei.    A  3,  white ;  B  10,  p<*le  blue,  with  a  compunioi. 
of  the  same  magnitude  and  color. 

2.  ft  CEPFIKI  (Alphirk)—A.  DOUBLE  STAR  on  the  left  side  of  the  girdle  of  Cepheus,  two 
thirds  of  the  distance  from  Polaris  to  Alderamin.    A  3,  white;  B  8,  blue,  with  a  very 
minute  double  star  preceding. 

8.  y  CBPHBF  (Er  Rai) — A  DOUBLE  STAR  in  the  knee  of  Cepheus,  with  a  distant  telescr/j  K 
companion  on  the  preceding  parallel.  A  3,  yellow;  B  14,  dusky.  R.  A.,  28h.  82m.  47s  „• 
Dec.,  N.  76°  44'  7".  This  star  will  be  the  Pole  star  in  about  2360  years. 


HISTORY.— Who  was  Cepl-«us  ?     Why  placed  in  the  heavens  ?     What  said  of  the  ongm 
of  other  constellations? 
TKLKSCOPIO  OBJECTS.— Alpha  ?    Bc-ta,  &c.?    What  clusters? 

B.Cr,  2 


28  ASTRONOMY. 

4.  0  CKPHII  (For)  in  the  crown  of  Cepheus,  a  fine,  though  wide  DOUBLB  STAR;  R.  A.  22h. 
28m.  14s. ;  Dec.,  N.  57°  35'  9*.    A  4}£,  orange  tint ;  B  7,  fine  blue — the  colors  in  fine  con- 
trast.   This  star  is  -variable,  with  a  period  of  5d.  Sh.  30m. 

5.  A  LARGK  AND  RICH  CLUSTER  on  the  left  elbow  ;  R.  A.,  20h.  2Sm.  17s. ;  Dec.,  N.  60*  06' 
2".    It  is  12*  due  north  of  a  Cygni;  and  8"  west-south-west  of  7?  Cephei.    "A  grand  but 
distant  collocation  of  suns  bound  together  by  mutual  relations." 

>>.  AN  IRREGULAR  CLUSTER  between  the  head  of  Cepheus  and  the  chain  of  Andromeda; 
R.  A.,  23h.  17m.  10s.;  Dec.,  N.  60*  43'  1".  It  is  about  one-third  of  the  distance-  from 
8  Cassiopese  to  a  Cephei ;  and  may  be  seen  on  Map  VI. f  near  the  sceptre  of  Cephcua 
For  a  telescopic  view,  see  Map  VIII.,  Fig.  24. 


CHAPTER  II. 

CONSTELLATIONS    ON   THE   MERIDIAN   IJ?    DECEMBER. 

AEIES  (THE  RAM).— MAP  II. 

50.  TWENTY-TWO  centuries  ago,  as  Hipparchus  informs  us, 
this  constellation  occupied  the  first  sign  in  the  ecliptic,  com- 
mencing at  the  vernal  equinox.  But  as  the  constellations  gain 
about  50"  on  the  equinox,  at  every  revolution  of  the  heavens,* 
they  have  advanced  in  the  ecliptic  nearly  31°  beyond  it,  or  more 
than  a  whole  sign  :  so  that  the  Fishes  now  occupy  the  same 
place  in  the  Zodiac,  that  Aries  did  in  the  time  of  Hipparchus  ; 
while  the  constellation  Aries  is  now  in  the  sign  Taurus,  Taurus 
in  Gemini,  and  Gemini  in  Cancer,  and  so  on. 

ARIES  is  therefore  now  the  second  constellation  in  the  Zodiac.  It  is  situated  next  east 
of  Pisces,  and  is  midway  between  the  Triangles  and  the  Fly  on  the  N.  and  the  head  of 
Oetus  on  the  S.  It  contains  66  stars,  of  which,  one  is  of  the  2d,  one  of  the  3d,  and  two  of 
tiie  4th  magnitudes. 

"  First,  from  the  east,  the  Ram  conducts  the  year ; 
Whom  Ptolemy  with  twice  nine  stars  adorns, 
Of  which  two  only  claim  the  second  rank ; 
The  rest,  when  Cynthia  fills  the  sign,  are  lost." 

Aries  is  readily  distinguished  by  means  of  two  bright  stars  in  the  head,  about  4*  apart, 
the  brightest  being  the  most  north-easterly  of  the  two.  The  first,  which  is  of  the  2d 
magnitude,  situated  in  the  right  horn,  is  called  Alpha  Arietis,  or  simply  Arietix;  the 
other,  which  is  of  the  3d  magnitude,  lying  near  the  left  horn,  is  called  Sheratan,  and  may 
be  known  by  another  star  of  the  4th  magnitude,  in  the  ear,  1  J$°  S.  of  it,  called  Mesarthim^ 
which  is  the  first  star  in  this  constellation. 

Arietia  and  Sheratan,  are  one  instance  out  of  many,  where  stars  of  more  than  ordinary 
brightness  are  seen  together  in  pairs,  as  in  the  Twins,  the  Little  Dog,  &c.,  the  brightest 
Star  being  commonly  on  the  east. 

*  See  "  Precession  of  the  Equinoxes,"  page  270. 

t'0.  Constellations  in  this  chapter  ?  Aries  22  centuries  ago  f  Now ;  and  why  t  How 
.lletinguished  ?  Arietis  and  Sheratan  ? 


ARIES.  29 

51.  The  position  of  Arietis  affords  important  facilities  to 
nautical  science.  Difficult  to  comprehend  as  it  may  be,  to  the 
unlearned,  the  skilful  navigator  who  should  be  lost  upon  an 
unknown  sea,  or  in  the  midst  of  the  Pacific  ocean,  could,  by 
measuring  the  distance  between  Arietis  and  the  Moon,  which 
often  passes  near  it,  determine  at  once  not  only  the  spot  he  was 
in,  but  his  true  course  and  distance  to  any  known  meridian  or 
harbor  on  the  earth.  See  Part  II.,  page  206. 

Arietis  comes  to  the  meridian  about  12  minutes  after  Shera- 
tan,  on  the  5th  December,  near  where  the  sun  does  in  midsum- 
mer. Arietis,  also,  is  nearly  on  the  same  meridian  with  Almaack, 
in  the  foot  of  Andromeda,  19°  N.  of  it,  and  culminates  only 
four  minutes  after  it.  The  other  stars  in  this  constellation  are 
quite  small,  constituting  that  loose  cluster  which  we  see  between 
the  Fly  on  the  north,  and  the  head  of  Cetus  on  the  south. 

When  Arietis  is  on  the  meridian,  Andromeda  and  Cassiopeia 
are  a  little  past  the  meridian,  nearly  overhead,  and  Perseus  with 
the  head  of  Medusa,  is  as  far  to  the  east  of  it.  Taurus  and 
Auriga  are  two  or  three  hours  lower  down  ;  Orion  appears  in 
the  S.  E.,  and  the  Whale  on  the  meridian,  just  below  Aries, 
while  Pegasus  and  the  Swan  are  seen  half-way  over  in  the  west. 

The  manner  in  which  the  ancients  divided  the  Zodiac  into  12  equal  parts,  was  both 
simple  and  ingenious.  Having  no  instrument  that  would  measure  time  exactly,  "  they 
took  a  vessel,  with  a  small  hole  in  the  bottom,  and  having  filled  it  with  water,  suffered  the 
same  to  distill,  drop  by  drop,  into  another  vessel  set  beneath  to  receive  it,  beginning  at 
the  moment  when  some  7tar  rose,  and  continuing  till  it  rose  the  next  following  night,  when 
it  would  have  performed  one  complete  revolution  in  the  heavens.  The  water  falling  down 
into  the  receiver  they  divided  into  twelve  equal  parts ;  and  having  twelve  other  small 
vessels  in  readiness,  each  of  them  capable  of  containing  one  part,  they  again  poured  all 
the  water  into  the  upper  vessel,  and  observing  the  rising  of  some  star  in  the  Zodiac,  at 
the  same  time  suffered  the  Mjater  to  drop  into  one  of  the  small  vessels.  And  as  soon  as  it 
was  full,  they  removed  it,  and  set  an  empty  one  in  its  place.  Just  as  each  vessel  was  full, 
they  took  notice  what  star  of  the  Zodiac  rose  at  that  time,  and  thus  continued  the  process 
through  the  year,  until  the  12  vessels  were  filled." 

Thus  the  Zodiac  was  divided  into  12  equal  portions,  corresponding  to  the  12  months  of 
the  year,  commencing  at  the  vernal  equinox.  Each  of  these  portions  served  as  the 
visible  representative  or  xign  of  the  month  it  appeared  in. 

All  those  stars  in  the  Zodiac  which  were  observed  to  rise  while  the  first  vessel  was  fill- 
ing, were  constellated  and  included  in  the  first  sign,  and  called  ArieK^  an  animal  held  in 
great  esteem  by  the  shepherds  of  Chaldea.  All  those  stars  in  the  Zodiac  which  rose  while 
the  second  vessel  was  filling,  were  constellated  and  included  in  the  second  sign,  which, 
for  a  similar  reason,  was  denominated  Taurux;  and  all  those  stars  which  were  observed 
to  rise  while  the  third  vessel  was  filling,  were  constellated  in  the  third  sign,  and  called 
Gemini,  in  allusion  to  the  twin  tseaxon  of  the  flocks. 

Thus  each  sign  of  30*  in  the  Zodiac,  received  a  distinctive  appellation,  according  to  the 
fancy  or  superstition  of  the  inventors ;  which  names  have  ever  since  been  retained, 
although  the  constellations  themselves  have  since  left  their  nominal  signs  more  than  30° 
behind.  The  sign  Aries,  therefore,  included  all  the  stars  embraced  in  the  first  80°  of  the 
Zodiac,  and  no  more.  The  sign  Taurus,  in  like  manner,  included  all  those  stars  embraced 


fit  Position  of  Arietis?  Importance  to  mariners?  When  come  to  meridian  ?  Where 
And  —- i*da  and  Cassiopeia  then  ?  Perseus  ?  Taurus,  Auriga,  Orion,  Pegasus  and  Swan  ? 
What  t.  other  stars  in  Aries?  Ancient  method  of  dividing  the  Zodiac?  Named  oi 
signs  If 


SO  ASTRONOM*. 

In  tue  next  30*  of  the  Zodiac,  or  those  between  30*  and  60%  and  so  of  the  rest.  Of  tho«e 
who  imagine  that  the  twelve  constellations  of  the  Zodiac  refer  to  the  twelve  tribe*  of 
Israel,  some  ascribe  Aries  to  the  tribe  of  Simeon,  and  others,  to  Gad. 

HISTORY. 

According  to  fable,  this  is  the  ram  which  bore  the  golden  fleece,  and  carried  Phryxus 
and  his  sister  Helle  through  the  air,  when  they  fled  to  Colchis  from  the  persecution  of  their 
stepmpther  Ino.  The  rapid  motion  of  the  ram  in  his  aerial  flight  high  above  the  earth, 
caused  the  head  of  Helle  to  turn  with  giddiness,  and  she  fell  from  his  back  into  that  part 
of  the  sea  which  was  afterwards  called  Hellespont,  in  commemoration  of  the  dreadful 
event.  Phryxus  arrived  safe  at  Colchis,  but  was  soon  murdered  by  his  own  father-in-law, 
35tes,  who  envied  him  his  golden  treasure.  This  gave  rise  to  the  celebrated  Argonautic 
expedition  under  the  command  of  Jason,  for  the  recovery  of  the  golden  fleece. 

Nephele,  Queen  of  Thebes,  having  provided  her  children,  Phryxus  and  Helle,  with  this 
noble  animal,  upon  which  they  might  elude  the  wicked  designs  of  those  who  sought  their 
life,  was  afterwards  changed  into  a  cloud,  as  a  reward  for  her  parental  solicitude  ;  and 
the  Greeks  ever  after  called  the  clouds  by  her  name.  But  the  most  probable  account  of 
the  origin  of  this  constellation  is  given  in  a  preceding  paragraph,  where  it  is  referred  to 
the  flocks  of  the  Chaldean  shepherds. 

During  the  campaigns  of  the  French  army  in  Egypt,  General  Dessaix  discovered  among 
the  ruins  at  Dendera,  near  the  banks  of  the  Nile,  the  great  temple  supposed  by  some  to 
have  been  dedicated  to  Isis,  the  female  deity  of  the  Egyptians,  who  believed  that  the  ris- 
ing of  the  Nile  was  occasioned  by  the  tears  which  she  continually  shed  for  the  loss  of  her 
brother  Osiris,  who  was  murdered  by  Typhon.  Others  suppose  this  edifice  was  erected 
for  astronomical  purposes,  from  the  circumstance  that  two  Zodiacs  were  discovered, 
drawn  upon  the  ceiling,  on  opposite  sides.  On  both  these  Zodiacs  the  equinoctial  points 
are  in  Leo,  and  not  in  Aries ;  from  which  it  has  been  concluded,  by  those  who  pertina- 
ciously endeavor  to  array  the  arguments  of  science  against  the  chronology  of  the  Bible 
and  the  validity  of  the  Mosaic  account,  that  these  Zodiacs  were  constructed  when  the  sun 
entered  the  sign  Leo,  which  must  have  been  9720  years  ago,  or  4000  years  before  the 
inspired  account  of  the  creation.  The  infidel  writers  in  France  and  Germany  make  it 
10,000  years  before.  But  we  may  "  set  to  our  seal,"  that  whatever  is  true  in  fact  and  cor- 
rect in  inference  on  this  subject  will  be  found,  in  the  end,  not  only  consistent  with  the 
Mosaic  record,  but  with  the  common  meaning  of  the  expressions  it  uses. 

The  discovery  of  Champollion  has  put  this  question  for  tver  at  rest ;  and  M.  Latroime, 
a  most  learned  antiquary,  has  very  satisfactorily  demonstrated  that  these  Egyptian 
Zodiacs  are  merely  the  horoscopes  of  distinguished  personages,  or  the  precise  situation 
of  the  heavenly  bodies  in  the  Zodiac  at  their  nativity.  The  idea  that  such  was  their  pur- 
pose and  origin,  first  suggested  itself  to  this  gentleman  on  finding,  in  the  box  of  a  mummy, 
a  similar  Zodiac,  with  such  inscriptions  and  characters  as  determined  it  to  be  the  horo- 
scope of  the  deceased  person. 

Of  all  the  discoveries  of  the  antiquary  among  the  relics  of  ancient  Greece,  the  ruins  o* 
Palmyra,  the  gigantic  pyramids  of  Egypt,  the  temples  of  their  gods,  or  the  sepulchres  of 
their  kings,  scarcely  one  so  aroused  and  riveted  the  curiosity  of  the  learned,  as  did  the 
discovery  of  Champollion  the  younger,  which  deciphers  tlie  hieroglyphics  of  ancient 
Egypt, 

The  potency  of  this  invaluable  discovery  has  already  been  signally  manifested  in  set- 
tling a  formidable  controversy  between  the  champions  of  infidelity  and  those  who  main- 
tain the  Bible  account  of  the  creation.  It  has  been  shown  that  the  constellation  Pificf^ 
since  the  days  of  Hipparchus,  has  come,  by  reason  of  the  annual  precession,  to  occupy 
the  same  apparent  place  in  the  heavens  that  Aries  did  two  thousand  years  ago.  The 
Christian  astronomer  and  the  infidel  are  perfectly  agreed  as  to  the  fact,  and  the  amount 
of  this  yearly  gain  in  the  apparent  motion  of  the  stars.  They  both  believe,  and  both  can 
demonstrate,  that  the  fixed  stars  have  gone  forward  in  the  Zodiac  about  50"  of  a  degree 
*n  every  revolution  of  the  heavens  since  the  creation ;  so  that  were  the  world  to  light 
upon  any  authentic  inscription  or  record  of  past  ages,  which  should  give  the  true  posi- 
tion or  longitude  of  any  particular  star  at  thai  time,  it  would  be  easy  to  fix  an  unques- 
tionable date  to  such  a  record.  Accordingly,  when  the  famous  "  Egyptian  Zodiacs," 
which  were  sculptured  on  the  walls  of  the  temple  at  Dendera,  were  brought  away  en 
*<«*•.«,  and  exhibited  in  the  Louvre  at  Paris,  they  enkindled  a  more  exciting  interest  in 
the  thousands  who  saw  them,  than  ever  did  the  entrance  of  Napoleon.  "  Educated  men 
«»f  every  order,  and  those- who  had  the  vanity  to  think  themselves  such,"  says  the  com- 
inentator  of  Champollion,  "  rushed  to  behold  tlw  Zodiacs.  These  Zodiacs  were  imme- 
diately published  and  commented  upon,  with  more  or  less  good  faitn  and  decorum. 

HISTORY.— Discovery  in  Egypt?  Use  made  of  the  Zodiacs?  What  did  they  prove  to 
be.  ?  How  ascertained  ?  Who  most  zealous  in  opposing  revelation  ?  Weans  employe-'.  1 


Science  struck  out  into  systems  very  bold  ;  and  the  spirit  of  infidelity,  seizing  upon  the 
discovery,  flattered  itself  with  the  hope  of  drawing  from  thence  new  support.  It  was 
unjustifiably  taken  for  granted,  that  the  ruins  of  Egypt  furnished  astronomy  with  monu- 
ments, containing  observations  that  exhibited  the  state  of  the  heavens  in  the  most 
remote  periods.  Starting  with  this  assumption,  a  pretence  was  made  of  demonstrating 
by  means  of  calculatlbns  received  as  infallible,  'that  the  celestial  appearances  assigned 
to  these  monuments  extended  back  from  forty-five  to  sixty-five  centuries;  that  the 
Zodiacal  system  to  which  they  must  belong,  dated  back  fifteen  thousand  years,  and  must 
reach  far  beyond  the  limits  assigned  by  Moses  to  the  existence  of  the  world."  Among 
those  who  stood  forth  more  or  less  bold  as  the  adversaries  of  Revelation,  the  most  pro- 
minent was  M.  Dupuis,  the  famous  author  of  L'origine  detous  left  Cultes. 

The  infidelity  of  Dupuis  was  spread  about  by  means  of  pamphlets,  and  the  advocates 
of  the  Mosaic  account  were  scandalized  "  until  a  new  Alexander  arose  to  cut  the  Gordian 
knot,  which  men  had  vainly  sought  to  untie.  This  was  Champollion  the  younger,  armed 
with  his  discovery."  The  hieroglyphics  now  speak  a  language  that  all  can  understand, 
and  no  one  gainsay.  "  The  Egyptian  Zodiacs,  then,"  says  Latronne,  "  relate  in  no  respect 
to  astronomy,  but  to  the  idle  phantasies  of  judicial  astrology,  as  connected  with  the  des- 
tinies of  the  emperors  who  made  or  completed  them." 

TELESCOPIC  OBJECTS. 

1.  a  ARIETIS— A  DOUBLE  STAR  in  the  Ram's  forehead;  R.  A.  Ih.  5Sm.  10s;  Dec.  N.  22* 
42'  02'.    A  3,  yellow;  B  11,  purple. 

Two  thousand  years  ago  the  first  meridian  or  Vernal  Equinox  passed  through  th* 
star-  but  the  recession  of  the  equinox  at  the  slow  rate  of  50"  per  year,  has,  in  that  lengtl 
of  time,  carried  the  equinoctial  nearly  60°  to  the  west,  where  we  now  find  it.  S>*e  thi. 
subject  explained  in  the  second  part  of  the  book. 

2.  /?  ARIETIS  (Sheratari) — A  BRIGHT  STAR  with  a  distant  companion  in  the  coil  of  the 
right  horn ;  R.  A.  In.  45m.  49s. ;  Dec.  N.  20'  01'  04'.    A  3,  pearly  white ;  B  11,  duskv. 

8.  y  ARIETIS  (Mesarthim)—*  DOUBLE  STAR  just  south  of/?;  R.  A.  Ih.  44m.  45s.;  Dec.  N. 
18'  30'  05'.  A  4}£,  bright  white ;  B  5,  pale  grey.  A  fine  object.  Map  VIII.,  Fig.  2. 

4.  e  ARIETIS — A  VERT  CLOSE  DOUBLE  STAR  near  the  root  of  the  tail,  and  between  it  and 
Musca;  R.  A.  2h.  50m.  04s.;  Dec.  N.  20*  41'  08".    A  5,  pale  yellow;  B  6J^,  whitish.    It 
requires  a  good  telescope  to  separate  them. 

5.  TT  ARIETIS — A  neat  TRIPLE  STAR  in  the  haunch,  about  one-third  of  the  distance  from 
ft  Arietis  to  Aldebaran ;  R.  A.  2h.  40m.  22s. ;  Dec.  N.  16"  47'  08".    A  5,  pale  yellow ;  B 
8^,  flushed ;  C  11,  dusky.    A  beautiful  trio. 

6.  A  QUADRUPLE  STAR  halfway  between  a  and  y  under  the  right  horn;"R.  A.  Ih.  50m. 
43s.;  Dec.  N.  20°  16'  07".    A  6,  topaz  yellow;  B  15,  deep  blue;  C  10,  lilac;  D,  pale  blue. 
An  exquisite  object. 

7.  A  ROUND  NEBULA  near  y  Arietis,  and  just  east  of  it;  R.  A.  Ih.  50m.  34s.;  Dec.  N 
18°  13'  06".    It  is  large  and  pale,  and  lies  among  some  small  stars,  some  of  which  form  a 
curve  across  She  south  part  of  the  field. 


TRIANGUL^E   (THE  TRIANGLES).— MAP  II. 

52.  The  Triangles  are  situated  between  the  head  of  Aries  on 
the  north,  and  the  feet  of  Andromeda  on  the  south.  R.  A. 
2h.;  Dec.  N.  30°.  They  contain  two  stars  of  the  4th  magni- 
tude, and  two  of  the  5th  ;  with  several  smaller.  A  line  from 
Sheratan  in  Aries,  to  Almaack,  will  pass  through  the  ludda 
Trianguli,  about  midway  between  them. 

TELESCOPIC  OBJECTS?    What  a  Arietis?     Other  double  stars?    Triple?    Quadruple? 
Any  clusters?     Nebulae? 
62.  Situation  of  the  Triangles  ?    Number  and  size  of  stars  ?     How  find  their  lucida  ? 


32  ASTRONOMY. 

HISTORY. 

The  upper  or  Northern  Triangle  is  one  of  the  ancient  46  asterisms;  and  Htvelius  took 
three  other  stars  between  it  and  the  head  of  Aries,  to  form  Triungutum  minus.  Tha 
latter  figure,  however,  is  discontinued,  though  shown  on  the  map. 

0 

TELESCOPIC  OBJECTS. 

1  a  TRIANGULI— A  bright  FOURTH  MAGNITUDE  STAR,  with  a  Telescopic  companion:  R.  A. 
Ih.  43m.  5Ss. ;  Dec.  N  28*  47'  OS".  A  fc  J$,  yellow ;  B  11,  lilac. 

2.  £  TRIANGCLI — A  MOST  DELICATE  DOUBLE  STAR  ;  R.  A.  Ih.  63m.  38s. :  Dec.  N.  82*  30'  05*. 
A  5)$,  bright  yellow  ;  B  15,  dusky. 

3.  A  large  and  distin  :t  but  faint  PALE  WHITE  NEBULA,  between  the  Triangles  and  the 
head  of  the  Northern  Fish ;  R.  A.  Ih.  24m.  51s. ;  Dec.  N.  29°  51*  03".    A  bright  star  a 
little  north-west,  and  five  others  more  remote  in  the  east. 


MUSOA   (THE  FLY).— MAP  II. 

53.  This  very  small  constellation  lies  directly  between  the 
back  of  Aries  on  the  south,  and  the  head  of  Medusa  on  the 
north.     It  has  one  star  of  the  2d,  two  of  the  4th,  and  two  of 
the  5th  magnitudes.     An  unimportant  asterism,  and  not  always 
mentioned  in  the  catalogues,  though  shown  on  the  map. 

TELESCOPIC  OBJECTS. 

1.  A  FIXE  DOUBLE  STAR  over  the  back  of  Aries,  nearly  midway  between  the  Pleiades  ana 
ft  Andromeda ;  R.  A.  2h.  31m.  20s. ;  Dec.  N.  26°  22'  02".    A  6,  pale  topaz ;  B  9,  light  blue. 
An  easy  object. 

2.  a  MUSCLE — a  COARSE  QUADRUPLE  STAR,  in  the  body  of  the  figure,  and  forming  its 
jucida ;  R.  A.  2h.  40m.  34s. ;  Dec.  N.  26°  35'  09".    A  3,  white ;  B  18,  deep  blue ;  C  11,  lurid; 
D  9,  pale  grey.    Both  these  objects  are  usually  classed  as  belonging  to  Aries. 

CETUS   (THE  WHALE).— MAP  II. 

54.  As  the  whale  is  the  chief  monster  of  the  deep,  and  the 
largest  of  the  aquatic  race,  so  is  it  the  largest  constellation  in 
the  heavens.     It  occupies  a  space  of  50°  in  length,  E.  and  W., 
with  a  m^an  breadth  of  20°  from  N.  to  S.     It  is  situated  below 
Aries  and  the  Triangles,  with  a  mean  declination  of  12°  S.     It 
ts  represented  as  making  its  way  to  the  E.,  with  its  body  below, 
•ind  its  head  elevated  above  the  equinoctial  ;  and  is  six  weeks  in 
massing  the  meridian.     Its  tail  comes  to  the  meridian  on  the  10th 
of  November,  and  its  head  leaves  it  on  the  22d  of  December. 

55.  This  constellation  contains  97  stars ;  two  of  the  2d  mag- 
nitude, ten  of  the  3d,  and  nine  of  the  4th.     The  head  of  Cetus 

HISTORY. — Which  ancient?    Who  formed  the  other?    Now  recognized,  or  not? 

TELESCOPIC  OBJECTS?     Double  stars?     Nebulae? 

53.  Sitii«Hon  of  Musca?  Stars?  Relative  importance?  Is  it  always  recognized  ae  a 
constellation  ?  54.  Cetus?  Comparative  size?  Situation?  How  represented? 
bo.  Numbei  of  stars  *  Magnitudes  ?  How  may  the  head  of  Cetius  be  known  ?  Brightest 


CETUS.  33 

way  be  readily  distinguished,  abcnt  20°  S.  E.  of  Aries,  by  means 
of  five  remarkable  stars,  4°  and  5°  apart,  and  so  situated  as  to 
form  a  regular  pentagon.  The  brightest  of  these  is  Menkar,  of 
the  2d  magnitude,  in  the  nose  of  the  Whale.  It  occupies  the 
S.  E.  angle  of  the  figure.  It  is  3^-°  N.  of  the  equinoctial,  and 
15°  E.  of  El  Rischa  in  the  bight  of  the  cord  between  the  Two 
Fishes.  It  is  directly  37°  S.  of  Algol,  and  nearly  in  the  same 
direction  from  the  Fly.  It  makes  an  equilateral  triangle  with 
Arietis  and  the  Pleiades,  being  distant  from  each  about  23°  S., 
and  may  otherwise  be  known  by  a  star  of  the  3d  magnitude  in 
the  mouth,  3°  W.  of  it,  called  Gamma,  placed  in  the  south  mid- 
dle angle  of  the  pentagon. 

56.  Nu  is  a  star  of  the  4th  magnitude,  4°  N.  W.  of  Gamma, 
and  these  two  constitute  the  S.  W.  side  of  the  pentagon  in  the 
bead  of  the  Whale,  and  the  N.  E.  side  of  a  similar  oblong  figure 
in  the  neck. 

Three  degrees  S.  S.  W.  of  Gamma,  is  another  star  of  the  3d 
magnitude  in  the  lower  jaw,  marked  Delta,  constituting  the  E. 
side  of  the  oblong  pentagon  ;  and  6°  S.  W.  of  this,  is  a  noted 
star  in  the  neck  of  the  Whale,  called  Mira,  or  the  "wonderful 
star  of  1596,"  which  forms  the  S.  E.  side.  This  variable  star 
was  first  noticed  as  such  by  Fabricius,  on  the  13th  of  August, 
1596.  It  changes  from  a  star  of  the  2d  magnitude  so  as  to 
become  invisible  once  in  234  days,  or  about  7  times  in  6  years. 
Herschel  makes  its  period  331  days,  10  hours,  and  19  minutes  ; 
while  Hevelius  assures  us  that  it  once  disappeared  for  4  years  ; 
so  that  its  true  period,  perhaps,  has  not  been  satisfactorily  deter- 
mined. 

The  whole  number  of  stars  ascertained  to  be  variable  amounts  to  only  15 ;  while  those 
which  are  suspected  to  be  variable,  amount  to  87. 

57.  Mira  is  7°  S.  S.  E.  of  El  Rischa,  in  the  bend  or  knot  of 
the  ribbon  which  connects  the  Two  Fishes.     Ten  degrees  S.  of 
Mira,  are  4  small  stars,  in  the  breast  and  paws,  about  3°  apart, 
which  form  a  square,  the  brightest  being  on  the  E.     Ten  degrees 
S.  W.  of  Mira  is  a  star  of  the  3d  magnitude,  in  the  heart, 
called  Baten  Kaitos,  which  makes  a  scalene  triangle  with  two 
other  stars  of  the  same  magnitude  7°  and  10°  W.  of  it ;  also, 
an  equilateral  triangle  with  Mira  and  the  easternmost  one  in 
the  square. 

0tar?  Position?  Name?  56.  Size  and  Position  of  Nu?  Delta?  Mira?  Position? 
Peculiarity?  When,  and  by  whom  first"  noticed  ?  Period  and  extent  of  variability? 
Whole  number  of  rariable  stars?  5T.  Baten  KcvUos?  Position  with  regard  to  Mira . 
r«  *ther  stars  ? 


34  ASTRONOMY. 

A  great  number  of  geometrical  figures  may  be  formed  from  the  stars  in  this,  and  In 
most  of  the  other  constellations,  merely  by  reference  .to  the  maps;  but  it  is  better  that 
the  student  should  exercise  his  own  ingenuity  in  thi's  way  with  reference  to  the  star* 
themselves,  for  when  once  he  has  constructed  a  group  into  any  letter  or  figure  of  his  own 
invention,  he  never  will  forget  it. 

The  teacher  should  therefore  require  his  class  to  commit  to  writing  the  result  of  their 
own  observations  upon  the  relative  position,  magnitude  and  figures  of  the  principal  stars 
in  each  constellation.  One  evening's  exercise  iu  this  way  will  disclose  to  the  student  a 
surprising  multitude  of  craws,  squares,  triangles,  arc*  and  letters,  by  which  he  will  be 
better  able  to  identify  and  remember  them,  than  by  any  instructions  that  could  be  given. 

For  example :  Mira  and  Baten  in  the  Whale,  about  10°  apart,  make  up  the  S.  E.  ot 
shorter  side  of  an  irregular  square,  with  El  Rischa  in  the  node  of  the  ribbon,  and  another 
star  in  the  Whale  as  far  to  the  right  of  Baten,  as  El  Rischa  is  above  Mira.  Again, 

There  are  three  stars  of  equal  magnitude,  forming  a  straight  line  W.  of  Baten ;  from 
which,  to  the  middle  star  is  10°,  thence  to  the  W.  one  12%  ;  and  8°  or  9°  S.  of  this  line, 
in  a  triangular  direction,  is  a  bright  star  of  the  second  magnitude  in  the  coil  of  the  tailt 
called  Diphda. 

In  a  southerly  direction,  25°  below  Diphda,  is  Alpha  in  the  head  of  the  Phenix,  and 
about  the  same  distance  S.  W.  is  ForaaLhaut,  in  the  mouth  of  the  Southern  Fish,  forming 
together  a  large  triangle,  with  Diphda  in  t!ie  vertex  or  top  of  it. 

That  fine  cluster  of  small  stars  S.  of  th«s  little  square  in  the  Whale,  constitutes  a  part 
of  a  new  constellation  called  the  ChynvitMl  Fumaoe.  The  two  stars  N.  E.,  and  the 
three  to  the  southward  of  the  little  square,  are  in  the  river  Eridwn/us, 

HISTORY. 

This  constellation  is  of  very  early  antiquity:  though  most  writers  consider  it  the 
famous  sea-monster  sent  by  Neptune  to  devour  Andromeda  because  her  mother  Cassio- 
peia had  boasted  herself  fairer  than  Juno  or  the  Sea  Nymphs ;  but  slain  by  Perseus  ana 
placed  among  the  stars  in  honor  of  his  achievement. 

"  The  winged  hero  now  descends,  now  soars, 
And  at  his  pleasure  the  vast  monster  gores. 
Deep  in  his  back,  swift  stooping  from  above, 
His  crooked  sabre  to  the  hilt  he  drove." 

It  is  quite  certain,  however,  that  this  constellation  had  a  place  in  the  heavens  long 
prior  to  the  time  of  Perseus.  When  the  equinoctial  sun  in  Aries,  which  is  right  over  the 
head  of  Cetus,  opened  the  year,  it  was  denominated  the  Preserver,  or  Deliverer,  by  the 
idolaters  of  the  East.  On  this  account,  according  to  Pausanius,  the  sun  was  worshipped, 
at  Eleusis,  under  the  name  of  the  Preserver  or  Saoiwtr. 

"  With  gills  pulmonic  breathes  the  enormous  whale, 
And  spouts  aquatic  columns  to  the  gale  ; 
Sports  on  the  shining  wave  at  noontide  hours, 
And  shifting  rainbows  crest  the  rising  showers." — Darwin. 

TELESCOPIC  OBJECTS. 

1.  /?  CETI— A  DOUBLE  STAR  ;  R.  A.  Oh.  35m.  84s. ;  Dec.  S.  18°  51'  9".  A  2%,  yellow ;  B  12, 
pale  blue. 

2.  y  CETI— A  CLOSE  DOUBLE  STAR  in  the  Whale's  mouth  ;  R.  A.  2h.  85m.  Ols. ;  Dec.  N. 
2"  83'  5".    A  3,  pale  yellow  ;  B  7,  lucid  blue  ;  the  colors  finely  contrasted. 

3.  v  A  DOUBLE  STAR  in  the  Whale's  eye ;  y  R.  A.  2h.  27m.  29s. ;  Dec.  N.  4*  53'  5'.  A  4J$, 
pale  yellow  ;  B  15,  blue. 

4.  ALONG  NARROW  NEBULA,  of  a  pale,  milky  tint;  R.  A.  Oh.  39m.  45s.;  Dec.  S.  26* 
10'  1".    It  is  situated  in  the  space  south  of  the  tail  of  Cetus,  near  a  line  drawn  from 
a  Andromeda  to  /3  Ceti.    Discovered  by  Miss  Herschel,  in  1783. 

5.  A  PLANETARY  NEBULA;  R.  A.  2h.  19m.  25s.;  Dec.  S.  1°  51'  6';  in  the  middle  of  the 
Whale's  neck. 

6.  A  BRIGHT  ROUND  NEBULA  ;  R.  A.  lh.  23m.  20s. ;  Dec.  S.  7°  41'  8*.    Registered  ly  Sir 
W.  Herschel,  1785.    It  is  just  above  the  Whale's  back. 

HISTORY. — Antiquity?  Its  original  name ?  When,  and  why?  What  worship  in  son- 
lequence  ? 

OBJECTS.— Beta?    Gamma?    Nu?    Nebulae? 


PERSEUS,    ET    CAPUT    MEDUSAE.  35 

T.  A  ROTTND  STELLAR  NEBCT.A,  near  d  in  the  Whale's  lower  jaw,  and  about  2%*  from  y, 
on  a  line  towards  €  ,  or  south  by  west.  A  very  distant  object,  classed  by  Sir  W.  Herschel, 
as  910  times  as  distant  as  stars  of  the  first  magnitude. 


PERSEUS,  ET  CAPUT  MEDUSA.— MAP  III.  A]STD  IY. 

58.  PERSEUS  is  represented  with  a  sword  in  his  right  hand, 
the  head  of  Medusa  in  his  left,  and  wings  at  his  feet.  It  is 
situated  directly  N.  of  the  Pleiades  and  the  Fly,  between 
Andromeda  on  the  W.  and  Auriga  on  the  E.  Its  mean  decli- 
nation is  46°  N.  It  is  on  the  meridian  the  24th  of  December. 
It  contains,  including  the  head  of  Medusa,  59  stars,  two  of 
which  are  of  the  2d  magnitude,  and  four  of  the  3d.  According 
to  Eudosia,  it  contains,  including  the  head  of  Medusa,  67  stars. 


Perseus  next, 


Brandishes  high  in  heaven  his  sword  of  flame, 
And  holds  triumphant  the  dire  Gorgon's  head, 
Flashing  with  fiery  snakes !  the  stars  he  counts 
Are  aixty-itt^Den  ;  and  two  of  these  he  boasts, 
Nobly  refulgent  in  the  second  rank — 
•»  One  in  his  vest,  one  in  Medusa's  head." 

59.  THE  HEAD  OF  MEDUSA  is  not  a  separate  constellation, 
out  forms  a  part  of  Perseus.  It  is  represented  as  the  trunkless 
head  of  a  frightful  Gorgon,  crowned  with  coiling  snakes,  instead 
of  hair,  which  the  victor  Perseus  holds  in  his  hand.  There  are, 
in  all,  about  a  dozen  stars  in  the  head  of  Medusa  ;  three  of  the 
4th  magnitude,  and  one,  varying  alternately  from  the  2d  to  the 
4th  magnitude.  This  remarkable  star  is  called  Algol.  It  is 
situated  12°  E.  of  Almaack,  in  the  foot  of  Andromeda,  and  may 
be  known  by  means  of  three  stars  of  the  4th  magnitude,  lying  a 
few  degrees  S.  W.  of  it,  and  forming  a  small  triangle.  It  is  on 
the  meridian  the  21st  of  December  ;  but  as  it  continues  above 
the  horizon  18  hours  out  of  24,  it  may  be  seen  every  evening 
from  September  to  May.  It  varies  from  the  2d  to  the  4th 
magnitude  in  about  3£  hours,  and  back  again  in  the  same  time ; 
after  which  it  remains  steadily  brilliant  for  2f  days,  when  the 
iame  changes  recur. 

The  periodical  variation  of  Algol  was  determined  in  1783,  by  John  Goodricke,  of  York 
(Eng.),  to  be  2  days,  20  hours,  43  minutes,  and  56  seconds.  Dr.  Herschel  attributes  th« 
variable  appearance  of  Algol  to  spots  upon  its  surface,  and  thinks  it  has  a  motion  on  its 
axis  sinrlar  to  that  of  the  #un.  He  also  observes,  of  variable  stars  generally: — "The 
rotary  motion  of  the  stars  upon  their  axis  is  a  capital  feature  in  their  resemblance  to 
the  sun.  It  appears  to  me  now,  that  we  cannot  refuse  to  admit  such  a  motion,  and  that 
indeed  it  may  be  as  evidently  proved  as  the  diurnal  motion  of  the  earth.  Dark  spots, 


58.  Perseus?  How  represented?  When  on  the  meridian?  Number  of  stars?  Size? 
59.  Head  of  Medusa?  How  represented?  Number  of  stars?  What  remarkable  cie? 
Situation?  Variableness  and  period?  When  and  by  whom  determined?  Supposed 
cause  of  variability  ?  Lalando  ? 

2* 


36  ASTRONOMY. 

or  larpe  portions  of  the  surface  less  luminous  than  the  rest,  turned  alternately  In  certain 
directions  either  toward,  or  from  us,  will  account  for  all  the  phenomena  of  periodical 
changes  in  the  lustre  of  the  stars,  so  satisfactorily,  that  we  certainly  need  not  look  out 
for  any  other  cause." 

It  is  said  that  the  famous  astronomer  Lalande,  who  died  at  Paris  in  1807,  was  wont  fr» 
remain  whole  nights,  in  his  old  age,  upon  the  Pont  Jfeuf,  to  exhibit  to  the  curious  the 
Variations  in  the  brilliancy  of  the  star  Algol. 

60.  Nine  degrees  E.  by  N.  from  Algol,  is  the  bright  star  Alge- 
nib,  of  the  2d  magnitude,  in  the  side  of  Perseus,  which  with  Al- 
maack,  makes  a  perfect  right  angle  at  Algol,  with  the  open  part 
towards  Cassiopeia.     By  means  of  this  strikingly  perfect  figure, 
the  three  stars  last  mentioned  may  always  be  recognized  without 
the  possibility  of  mistaking  them.     Algenib  may  otherwise  be 
readily  distinguished  by  its  being  the  brightest  and  middle  one 
of  a  number  of  stars  lying  four  and  five  degrees  apart,  in  a  large 
semicircular  form,  curving  towards  Ursa  Major. 

Algenib  comes  to  the  meridian  on  the  21st  December,  15  minutes  after  Algol,  at  which 
time  the  latter  is  almost  directly  overhead.  When  these  two  stars  are  on  the  meridian, 
that  beautiful  cluster,  the  Pleiades,  is  about  half  an  hour  E.  of  it;  and  in  short,  the 
most  brilliant  portion  of  the  starry  heavens  is  then  visible  in  the  eastern  hemisphere. 
The  glories  of  the  scene  are  unspeakably  magnificent;  and  the  student  who  fixes  his 
eye  upon  those  lofty  mansions  of  being,  cannot  fail  to  covet  a  knowledge  of  their  order 
and  relations,  and  to  "  reverence  Him  who  made  the  Seven  Stars  and  Orion." 

61.  The  Milky  Way  around  Perseus  is  very  vivid,  being  undoubt- 
edly a  rich  stratum  of  fixed  stars,  presenting  the  most  wondei  - 
ful  and  sublime  phenomenon  of  the  Creator's  power  and  great- 
ness.    Kohler,  the  astronomer,  observed  a  beautiful  nebula  near 
the  face  of  Perseus,  besides  eight  other  nebulous  clusters  in  dif- 
ferent parts  of  the  constellation. 

The  head  and  sword  of  Perseus  are  exhibited  on  the  circumpolar  map.  That  very 
bright  star  23*  E.  of  Algol,  is  Capella  in  the  Charioteer. 

HISTORY 

Perseus  was  the  son  of  Jupiter  and  Danae.  He  was  no  sooner  born  than  he  was  cast 
Into  the  sea,  with  his  mother  ;  but  being  driven  on  the  coasts  of  one  of  the  islands  of  the 
Cyclades,  they  were  rescued  by  a  fisherman,  and  carried  to  Polydectes,  the  king  of  the 
place,  who  treated  them  with  great  humanity,  and  intrusted  them  to  the  care  of  the 
priests  of  Minerva's  temple.  His  rising  genius  and  manly  courage  soon  made  him  a 
favorite  of  the  gods.  At  a  great  feast  of  Polydectes,  all  the  nobles  were  expected  to 
present  the  king  with  a  superb  and  beautiful  horse  ;  but  Perseus,  who  owed  his  benefac- 
tor much  not  wishing  to  be  thought  less  munificent  than  the  rest,  engaged  to  bring  him 
the  head  of  Medusa,  the  only  one  of  the  three  Gorgons,  who  was  subject  to  mortality. 
The  names  of  the  other  two  were  Stheno  and  Euryale.  They  were  represented  with  ser- 
pents wreathing  round  their  heads  instead  of  hair,  having  yellow  wings  and  brazen 
hands ;  their  bodies  which  grew  indissolubly  together,  were  covered  with  impenetrable 
ecales,  and  their  very  looks  had  the  power  of  turning  into  stones  all  those  on  whom 
they  fixed  their  eyes. 

To  equip  Perseus  for  this  perilous  enterprise,  Pluto,  the  god  of  the  infernal  regions, 
fent  him  his  helmet,  which  had  the  power  of  rendering  the  wearer  invisible.  Minerva, 
the  goddess  of  wisdom,  furnished  him  with  her  buckler,  which  was  as  resplendent  as  a 
polished  mirror  ;  and  he  received  from  Mercury  wings  for  his  feet,  and  a  dagger  made 

60.  Algenib?  How  known?  When  on  the  meridian?  Where,  then,  are  the  PI  siades? 
What  the  general  aspect  of  the  heavens?  61.  Milky  Way  around  Perseus?  Observa  • 
lion  of  Kohler? 

.— Wno  was  Perseus?    What  fate  at  birth,  &c.f 


PERSEUS,    ET    CAPUT    MEDUSAE.  3*5 

af  dIav«***Jk     Thus  equipped,  he  mounted  into  the  air,  conducted  by  Mir  erva,  and  came 
upon  tl.c  n.iAisters  who,  with  the  watchful  snakes  about  their  heads,  were  all  asleep.    He 
approached  thorn,  and  with  a  courage  which  amazed  and  delighted  Minerva,  cut  off  with 
one  blow  Medusa's  head.    The  noise  awoke  the  two  immortal  sisters,  but  Pluto's  helmet 
rendered  Perseus  invisible,  and  the  vengeful  pursuit  of  the  Gorgons  proved  fruitless. 
"  In  the  mirror  of  his  polished  shield 
Reflected,  saw  Medusa  slumbers  take, 
And  not  one  serpent  by  good  chance  awake  ; 
Then  backward  an  unerring  blow  he  sped, 
And  from  her  body  lopped  at  once  her  head." 

Perseus  then  made  his  way  through  the  air,  with  Medusa's  head  yet  reeking  in  his> 
band,  and  from  the  blood  which  dropped  from  it  as  he  flew,  sprang  all  those  innumerable 
serpents  that  have  ever  since  infested  the  sandy  deserts  of  Libya. 
"  The  victor  Perseus,  with  the  Gorgon  head, 
O'er  Libyan  sands  his  airy  journey  sped, 
The  gory  drops  distilled,  as  swift  he  flew, 
And  from  each  drop  envenomed  serpents  grew." 

The  destruction  of  Medusa  rendered  the  name  of  Perseus  immortal,  and  he  waa 
changed  into  a  constellation  at  his  death,  and  placed  among  the  stars,  with  the  head  of 
Medusa  by  his  side. 

TELESCOPIC  OBJECTS. 


1.  a  PERSEI—  A  FINE  DOUBLE  STAR  ;  R.  A.  3h.  12m.  55s.  ;  Dec.  N.  49°  IT  2".    A  2j£,  bril- 
liant  lilac  ;  B  9,  cinereous.     This  is  Algenib,  in  the  hero's  left  side. 

2.  ft  PERSEI,  or  Algol;  R.  A.  2h.  57m.  46s.  ;  Dec.  N.  41*  20*.    A  variable  DOUBLE  STAR. 
A  2  to  4,  whitish  ;  B  11,  purple.    The  former  varies  in  brightness  periodically,  from  the 
2d  to  the  4th  magnitude,  and  back  again  to  the  2d  magnitude,  period  being  2d.  20h.48m. 
56s.  ;  an  object  of  great  interest. 

3.  y  PERSEI—  A  WIDE  UNEQUAL  DOUBLE  STAR  in  the  hero's  left  shoulder:  R.  A.  2h.  53m. 
14s.  ;  Dec.  N.  52*  52'  4'.    A  4,  flushed  white  ;  B  14,  clear  blue. 

4.  6  PERSEI—  A  BRIGHT  STAR  with  a  companion  in  the  hero's  hip;  R.  A.,  3h.  31m.  33s.; 
Dec.,  N.  47*  16'  2".    About  3"  south-west  of  a  Persei.    A  3%,  white  ;  B  11,  pale  blue. 

5.  f  PERSEI—  A  NEAT  DOUBLE  STAR  in  the  right  knee  ;    R.  A.  8h.  47m.  08s.  ;  Dec.  N.  89* 
82'  4".    A  3^,  pale  white  ;  B  9,  lilac  ;  a  fine  delicate  object. 

6.  £  PERSEI—  A  DELICATB  QUADRUPLE  STAR  ;  R.  A.  3h.  44m.  05s.  ;   Dec.  N.  81*  24'  2". 
A  3%,  flushed  white;  B  10,  smalt  blue;  C  12,  ash-colored  ;  D  11,  blue.    It  is  situated  in 
the  right  foot,  and  is  designated  by  Smyth  as  "  an  elegant  group." 

7.  7?  PERSEI-A  FINK  DOUBLE  STAR  in  the  head  of  the  figure  ;  R.  A.  2h.  39m.  04s.  ;  Dec. 
N.  55"  13'  5".    A  5,  orange  ;  B  8Jg,  smalt  blue  ;  the  colors  in  fine  contrast. 

8.  A  GORGEOUS  CLUSTER  in  the  sword  handle  of  Perseus  ;  R.  A.  2h.  08m.  58s.  ;  Dec.  N. 
56°  24'  4".    It  may  be  seen  with  the  naked  eye,  and  when  seen  through  a  good  telescope, 
is  one  of  the  most  magnificent  objects  in  the  heavens.    Map  VIII.,  Fig.  25. 

9.  An  EXTENSIVE  AND  RICH  CLUSTER  on  the  right  side  of  Perseus,  in  a  rich  portion  of 
the  galaxy.    R.  A.  8h.  04m.  Ols.;  Dec.  N.  46'  87'  9".    Smyth  says  "it  has  a  gathering 
epot  about  4'  in  diameter,  where  the  star-dust  glows  among  minute  points  of  light." 
Herschel  says,  "  the  large  stars  are  arranged  in  lines  like  interwoven  letters. 

10.  An  ELONGATED  NEBULA  ;  R.  A.  2h.  30m.  25s.;  Deo.  N.  38'  21'  3"  ;  supposed  to  be  a 
vast  ring,  seen  obliquely.    Map  VIII.,  Fig.  26. 

11.  A  pretty  compressed  OVAL  GROUP  OF  STARS,  in  the  left  knee  of  Perseus,  nearly  mi  J- 
iray  between  A  and  //;  R.  A.  3h.  58m.  11s.;  Dec.  N.  49*  04'  05".    A  well-marked  object, 
surrounded  by  a  curve  of  larger  stars,  somewhat  in  the  form  of  the  letter  D.  Map  VIII., 
Fig.  27. 

TELESCOPIC  OBJECTS.—  Alpha  ?     Beta?     Gamma?     Delta?     Epsilon?     Zeta?     Eta? 
Clusters  ?    Nebula?    Which  shown  on  the  map? 


<9  ASTRONOMY. 

CHAPTER  III. 

CONSTELLATIONS    ON   THE    MERIDIAN    IN   JANUARY. 

TAURUS  (THE  BULL).— MAP  III. 

62.  TAURUS  is  represented  in  an  attitude  of  rage,  as  if  about 
to  plunge  at  Orion,  who  seems  to  invite  the  onset  by  provoca^ 
tions  of  assault  and  defiance.     Only  the  head  and  shoulders  of 
the  animal  are  to  be  seen ;   but  these  are  so  distinctly  marked 
that  they  caimot  be  mistaken. 

The  constellations  which  pass  our  meridian  in  the  months  of  January,  February  and 
March,  present  to  us  the  most  brilliant  and  interesting  portion  of  the  heavens ;  embrac- 
ing an  annual  number  of  stars  of  the  highest  order  and  brightness,  all  so  conspicuously 
situated,  that  the  most  inexperienced  can  easily  trace  them  out. 

63.  Taurus  is  now  the  second  sign  and  third  constellation  of  the 
Zodiac ;   but  anterior  to  the  time  of  Abraham,  or  more  than 
4000  years  ago,  the  vernal  equinox  took  place,  and  the  year 
opened  when  the  sun  was  in  Taurus;  and  the  Bull,  for  the  space 
of  2000  years,  was  the  prince  and  leader  of  the  celestial  host. 
The  Ram  succeeded  next,  and  now  the  Fishes  lead  the  year. 
The  head  of  Taurus  sets  with  the  sun  about  the  last  of  May, 
when  the  opposite  constellation,  the  Scorpion,  is  seen  to  rise  in 
the  S.  E.     It  is  situated  between  Perseus  and  Auriga  on  the 
north,  Gemini  on  the  east,  Orion  and  Eridanus  on  the  south,  and 
Aries  on  the  west,  having  a  mean  declination  of  16°  N. 

64.  Taurus  contains  141  visible  stars,  including  two  remark- 
able clusters  called  the  PLEIADES  and  HYADES.     The  first  is  now 
on  the  shoulder,  and  the  latter  in  the  face  of  the  Bull.     The 
names  of  the  Pleiades   are  Alcione,  Merope,  Maia,   Electra, 
Tayeta,  Sterope  and  Celeno.     Merope  was  the  only  one  who 
married  a  mortal,  and  on  that  account  her  star  is  dim  among  her 
sisters.     Although  but  six  of  these  are  visible  to  the  naked  eye, 
yet  Dr.  Hook  informs  us  that,  with  a  twelve  feet  telescope,  he 
8aw  78  stars;    and  Rheita  affirms  that  he  counted  200  stars  in 
this  small  cluster.     For  its  appearance  through  an  ordinary  tele- 
scope, see  Map  VIII.,  Fig.  28. 

The  most  ancient  authors,  such  as  Homer,  Attains,  and  Geminus,  counted  only  *?'ca 
Pleiades;  but  Simonides,  Varro,  Pliny,  Aratus,  Hipparchus,  and  Ptolemy,  reckon  them 

62.  How  is  Taurus  represented ?  How  much  of  him  seen?  What  constellations  most 
brilliant?  J68.  In  what  sign  is  Taurus  ?  What  constellation  ?  How  4000  years  ago? 
What  next  led  the  year?  What  now?  At  what  time  does  Taurus  set  with  the  sun? 
Row  situated?  64.  How  many  visible  stars  in  Taurus?  Clusters?  How  situated? 
Names  of  the  Pleiades?  What  said  of  Merope?  How  many  of  the  Pleiades  visibl*  to 
the  naked  eye?  Dr.  Hook  and  Rheita?  Ancient  authors? 


TAURUS.  .<9 

leven  in  number;  and  it  was  asserted,  that  the  seventh  had  been  seen  before  the  burn- 
ing of  Troy ;  but  this  difference  might  arise  from  the  difference  in  distinguishing  them 
with  the  naked  eye. 

65.  The  Pleiades  are  so  called  from  the  Greek  word,  rrXeeiv 
pkein,  to  sail;   because  at  this   season  of  the  year,  they  were 
considered  "the  star  of  the  ocean"  to  the  benighted  mariner. 

Yirgil  who  flourished  1200  years  before  the  invention  of  the  magnetic  needle,  says 
that  the  stars  were  relied  upon,  in  the  first  ages  of  nautical  enterprise,  to  guide  the  rude 
bark  over  the  seas. 

"Tune  alnos  primum  fluvii  sensere  cavatas ; 
Navita  turn  stellis  numeros,  et  nomina  fecit, 
Pleiadas,  Hyadas,  claramque  Lycaonis  Arcton." 
"  Then  first  on  seas  the  shallow  alder  swam  ; 
Then  sailors  quarter'd  heaven,  and  found  a  name 
For  every  fix'd  and  every  wand'ring  star — 
The  Pleiades,  Hyades,  and  the  Northern  Car." 

The  same  poet  also  ,.  escribes  Palinurus,  the  renowned  pilot  of  the  Trojan  fleet,  as 
watching  the  face  of  the  nocturnal  heavens. 

"Sidera  cuncta  notat  tacito  labentia  ccelo, 
Arcturum,  pluviasque  Hyadas,  geminosque  Triones, 
Armatumque  auro  circumspicit  Orioua." 
*•  Observe  the  stars,  and  notes  their  sliding  course, 
Ihe  Pleiades,  Hyades,  and  their  wat'ry  force; 
And  both  the  Bears  is  careful  to  behold, 
And  bright  Orion,  arm'd  with  burnished  gold." 

Indeed,  this  sagacious  pilot  was  once  so  intent  in  gazing  upon  the  stars  while  at  the 
helm,  that  he  fell  overboard,  and  was  lost  to  his  companions. 

"  Headlong  he  fell,  and  struggling  in  the  main, 
Cried  out  for  helping  hands,  but  cried  in  vain." 

66.  Alcyone,  of  the  3d  magnitude,  being  the  brightest  star  in 
this  cluster,  is  sometimes  called  the  light  of  the  Pleiades.     The 
other  five  are  principally  of  the  4th  and  5th  magnitudes.     The 
Pleiades,  or,  as  they  are  more  familiarly  termed,  the  seven  stars, 
come  to  the  meridian  10  minutes  before  9  o'clock,  on  the  even- 
ing of  the  1st  of  January,  and  may  serve  in  place  of  the  sun,  to 
indicate  the  time,  and  as  a  guide  to  the  surrounding  stars. 

According  to  Hesiod,  who  wrote  about  900  years  before  the  birth  of  our  Savior,  thf 
heliacal  rising  of  the  Pleiades  took  place  on  the  llth  of  May,  about  the  time  of  harvest 
"  When,  Atlas-born,  the  Pleiad  stars  arise 
Before  the  sun  above  the  dawning  skies, 
'Tis  time  to  reap  ;  and  when  they  sink  below 
The  morn-illumined  west,  'tis  time  to  sow." 

Thus,  in  all  ages,  have  the  stars  been  observed  by  the  husbandman,  for  "  signs  and 
for  seasons." 

Pliny  says  that  Thales,  the  Miletan  astronomer,  determined  the  cosmical  setting  of 
the  Pleiades  to  be  25  days  after  the  autumnal  equinox.  This  would  make  a  difference 
between  the  setting  at  that  time  and  the  p)-esent,  of  35  days,  and  as  a  day  answers  to 
about  59'  of  the  ecliptic,  these  days  will  make  34*  25'.  This  divided  by  the  annual  pre- 
cession (50ii"),  will  give  2465  years  since  the  time  of  Thales.  Thus  does  astronomy 
become  the  parent  of  chronology. 


65.  Why  Pleiades  so  called?  Remark,  and  quotations  from  Virgil?  66.  What  said 
of  Alcyone  ?  Of  the  ^t.her  five  ?  When  on  the  meridian  ?  Serve  what  purpose  ?  Period, 
and  remark  of  Hesiod?  Of  Pliny?  What  calculation  respecting  the  pasiage  of  tbft 
Ple;a<lc»  ^ver  the  meridian  ? 


40  ASTRONOMY. 

If  it  be  borne  in  mind  that  the  stars  uniformly  rise,  come  to  the  meridian,  and  set  abont 
four  minutes  earlier  every  succeeding  night,  it  will  be  very  easy  to  determine  at  what 
time  the  seven  stars  pass  the  meridian  on  any  night  subsequent  or  antecedent  to  the 
1st  of  January.  For  example :  at  what  time  will  the  seven  stars  culminate  on  the  5th 
of  January  ?  Multiply  the  5  days  by  4,  and  take  the  result  from  the  time  they  culminate 
en  the  1st,  and  it  will  give  30  minutes  after  8  o'clock  in  the  evening. 

67.  The  Pleiades  are  also  sometimes  called  Vergilia,  or  th« 
"  Virgins  of  Spring  •"  because  the  sun  enters  this  cluster  in  the 
"  season  of  blossoms/7  about  the  18th  or  May.     He  who  made 
them  alludes  to  this  circumstance  when  he  demands  of  Job  : 
"  Canst  thou  bind  the  sweet  influences  of  the  Pleiades,"  &c  — 
(Job  38  :  31.) 

The  Syrian  name  of  the  Pleiades  is  Succotk,  or  Succoth-Benoth,  derived  from  a  Chai- 
daic  word,  which  signifies  "  to  speculate,  to  observe,"  and  the  "  Men  of  Succ^th" 
(2  Kings  17 :  30)  have  been  thence  considered  observers  of  the  stars. 

68.  The  Hyades  are  situated  11°  S.  E.  of  the  Pleiades,  in  the 
face  of  the  Bull,  and  may  be  readily  distinguished  by  means  of 
five  stars  so  placed  as  to  form  the  letter  Y.     (Map  YIIL,  Fig. 
29.)     The  most  brilliant  star  is  on  the  left,  in  the  top  of  the 
letter,  and  called  Aldebaran  ;  from  which  the  moon's  distance  is 
computed. 

"  A  star  of  the  first  magnitude  illumes 
His  radiant  head  ;  and  of  th«  second  rank, 
Another  beams  not  far  remote." 

The  ancient  Greeks  counted  seven  in  this  cluster : — 

"  The  Bull's  head  shines  with  seven  refulgent  flames, 
Which,  Grecia,  Hyades,  from  their  ^lowering  names." 

69.  Aldebaran  is  of  Arabic  origin,  and  takes  its  name  from 
two  words  which  signify,  "  He  went  before,  or  led  the  way" — 
alluding  to  that  period  in  the  history  of  astronomy  when  this 
Btar  led  up  the  starry  host  from  the  vernal  equinox.     It  comes 
to  the  meridian  at  9  o'clock   on  the   10th  of  January,  or  48-| 
minutes  after  Alcyone,  on  the  1st.     When  Aries  is  about  27° 
high,  Aldebaran  is  just  rising  to  the  east.     So  MANILIUS  : — 

"  Thus,  when  the  Ram  hath  doubled  ten  degrees, 

And  join'd  seven  more,  then  rise  the  Hyades." 

A  line  15^'  E.  N.  E.  of  Aldebaran  will  point  out  a  bright  star  of  the  2d  magnitude  in 
the  extremity  of  the  northern  horn,  marked  Beta  or  El  Nath  ;  (this  star  is  also  in  the 
foot  of  Auriga,  and  is  common  to  both  constellations.)  From  Beta  in  the  northern  horn, 
to  Zeta,  in  the  tip  of  the  southern  horn,  it  is  8%  in  a  southerly  direction.  This  star 
forms  a  right  angle  with  Aldebaran  and  Beta.  Beta  and  Zeta,  then,  in  the  button  of  the 
horns,  are  in  a  line  nearly  north  and  south,  8°  apart,  with  the  brightest  on  the  north 
That  very  bright  star  17%°  N.  of  Beta,  is  Capetta,  in  the  constellation  Auriga, 

G7.  What  other  name  have  the  Pleiades,  and  why  ?  Citation  from  Job  ?  Syrian  name  ? 
68.  Where  are  the  Hyades  situated?  How  known?  Where  the  most  brilliant  star? 
Name  ?  Are  they  shown  on  the  map  ?  69.  Origin  and  import  of  the  name  Aldebaran  f 
When  does  it  come  to  the  meridian  at  9  o'clock  p.m.  ?  Where  is  Beta?  In  wi.at  other 
constellation  ?  Zeta,  and  its  distance?  How  situated  wilh  reference  to  AKibarar  anJ 
Beta?  How  Beta  and  Zeia ?  Capeua? 


ORION.  41 

HISTORY. 

According  to  the  Grecian  mythology,  this  is  ibz  animal  which  bore  Europa  over  th» 
•eas  to  that  country  which  derived  from  her  its  name.  She  was  the  daughter  of  Ageaor 
and  princess  of  Phrenicia.  She  was  so  beautiful  that  Jupiter  became  enamoured  of  her 
and  assuming  the  shape  of  a  snow-white  bull,  he  mingled  with  the  herds  of  Agenor, 
while  Europa,  with  her  female  attendants,  were  gathering  flowers  in  the  meadows. 
Europa  care-'sed  the  beautiful  animal,  and  at  last  had  the  courage  to  sit  upon  his  back. 
The  god  now  took  advantage  of  her  situation,  and  with  precipitate  steps  retired  towards 
the  shore,  and  crossed  the  sea  with  Europa  upon  his  back,  and  arrived  safe  in  Crete. 
Some  suppose  she  lived  about  1552  years  before  the  Christian  Era.  It  is  probable,  however, 
that  this  constellation  had  a  place  in  the  Zodiac  before  the  Greeks  began  to  cultivate  a 
knowledge  of  the  stars ;  and  that  it  was  rather  an  invention  of  the  Egyptians  or  Chal- 
deans. Both  the  Egyptians  and  Persians  worshipped  a  deity  under  this  figure,  by  the 
name  of  Apis ;  and  Belzoni  is  said  to  have  found  an  embalmed  bull  in  one  of  the  notable 
sepulchres  near  Thebes. 

In  the  Hebrew  Zodiac,  Taurus  is  ascribed  to  Joseph. 

The  Pleiades,  according  to  fable,  were  the  seven  daughters  of  Atlas  and  the  nympn 
Pleione,  who  were  turned  into  stars,  with  their  sisters  the  Hyades,  on  account  of  their 
ftmiable  virtues  and  mutual  affection. 

Thus  we  everywhere  find  that  the  ancients,  with  all  their  barbarism  and  idolatrj, 
entertained  the  belief  that  unblemished  virtue  and  a  meritorious  life  would  meet  their 
reward  in  the  sky.  Thus  Virgil  represents  Magnus  Apollo  as  bending  from  the  sky  to 
address  the  youth  lulus : — 

"Macte  nova  virtute  puer;  sic  itur  ad  astra; 
Diis  genite,  et  geniture  Deos." 

"  Go  on,  spotless  boy,  m  the  paths  of  virtue  ;  it  is  the  way  to  the  stars ;  offspring  of 
the  gods  thyself — so  shalt  thou  become  the  father  of  gods." 

Our  disgust  at  their  superstitions  may  be  in  some  measure  mitigated,  by  seriously 
reflecting,  that  had  some  of  these  personages  lived  in  our  day,  they  had  been  orna- 
ments in  the  Christian  Church,  and  models  of  social  virtue. 

TELESCOPIC    OBJECTS. 

1.  a  TACRI  (Aldebarari) — A  star  of  the  first  magnitude  with  a  telescopic  companion 
R.  A.  4h.  26m.  44s. ;  Dec.  N.  16°  10'  9".     A  1,  pale  rose  tint ;  B  12,  sky  blue. 

2.  @T\URi(El  Nath)—R.  A.  5h.  16m.  11s.;  Dec.  N.  28°  28'.     A  fine  star,  with  a 
distant  companion.     A  2,  brilliant  white  ;  B  10,  pale  grey. 

8.  y  TAURI— One  of  the  Hyades  ;  R.  A.  4h.  10m.  41s. ;  Dec.  11*  14'  1".  A  bright  star, 
with  a  distant  telescopic  companion  ;  A  3J£,  yellow ;  B  11,  pale  blue. 

4.  77  TAURI  (Alcyone)— One  of  the  Pleiades;   R.  A.  3h.  37m.  57s.;   Dec.  N.  23*  36'  3'. 
A  3,  greenish  yellow ;  B,  pale  white  and  distant. 

5.  A  NEBULOUS  STAR;  R.  A.  8h.  59m.  06*. ;    Dec.  N.  30*  20'  5'.    A  star  of  the  eighth 
magnitude,  with  a  faint  luminous  atmosphere  surrounding  it,  and  about  3'  in  diameter. 
This  star  and  nebula  led  Sir  William  Herschel  to  adopt  his  Nebula  Theory,  or  theory  of 
condensation  of  gas  or  nebulous  matter,  into  suns  and  worlds. 

6.  A  LARGE  NEBULA  ;   R.  A.  5h.  24m.  51s. ;   Dec.  N.  21°  54'  2'.    It  is  about  one  degree 
tiorth-west  of  £  in  the  tip  of  the  Bull's  southern  horn.     It  is  an  oval  form,  with  several 
minute  telescopic  stars  in  its  vicinity.     For  drawing,  see  Map  VIII.,  .Fig  30. 

Of  the  Pleiades  and  Ilyades,  two  prominent  clusters,  we  have  spoken  at  64,  65. 


.— MAP  III. 1 

70.  Whoever  looks  up  to  this  constellation  and  learns  its 
aame,  will  never  forget  it.  It  is  too  beautifully  splendid  to  need 
a  description.  When  it  is  on  the  meridian,  there  is  then  above 

H'STORY. — Story  of  Europa  and  Jupiter?  What  probability?  What  said  of  the 
Egyptians  and  Persians?  Hebrew  zodiacs?  Fabulous  paternity  of  the  Pleiades?  Why 
iurned  into  stars?  WThat  remarks  respecting  the  ancients? 

TELESCOPIC  OBJKCTS. — Alpha?  Beta?  Gamma?  Eta?  Nebulae?  Point  out  on  the 
map. 

70.  What  Is  said  of  Orion?    Of  the  view  when  on  the  meridian?    How  is  Cnon  repr*. 


42  ASTRONOMY. 

the  horizon  the  most  magnificent  view  of  the  celestial  bodies 
that  the  starry  firmament  affords  ;  and  it  is  visible  to  all  the 
habitable  world,  because  the  equinoctial  passes  through  the 
middle  of  the  constellation.  It  is  represented  on  celestial  maps 
by  the  figure  of  a  man  in  the  attitude  of  assaulting  the  Bull, 
with  a  sword  in  his  belt,  a  huge  club  in  his  right  hand,  and  the 
skin  of  a  lion  in  his  left,  to  serve  for  a  shield. 

Manilius,  a  Latin  poet,  who  composed  five  books  on  astronomy  a  short  time  before  the 
birth  of  our  Saviour,  thus  describes  its  appearance  : — 

"  First  next  the  Twins,  see  great  Orion  rise, 
His  arms  extended  stretch  o'er  half  the  skies ; 
His  stride  as  large,  and  with  a  steady  pace 
He  marches  on,  and  measures  a  vast  space  ; 
On  each  broad  shoulder  a  bright  star  display'd, 
And  three  obliquely  grace  his  hanging  blade. 
In  his  vast  head,  hnmers'd  in  boundless  spheres, 
Three  stars,  less  bright,  but  yet  as  great,  he  bears, 
But  farther  off  removed,  their  splendor's  lost ; 
Thus  graced  and  arm'd  he  leads  the  starry  host." 

71.  The  centre  of  the  constellation  is  midway  between  the 
poles  of  the  heavens  and  directly  over  the  equator.     It  is  also 
about  8°  W.  of  the  solstitial  colure,  and  comes  to  the  meridian 
about  the  23d  of  January.     The  whole  number  of  visible  stars 
in  this  constellation  is  78  ;  of  which,  two  are  of  the  first  magni- 
tude, four  of  the  2d,  three  of  the  3d,  and  fifteen  of  the  4th. 

72.  Those  four  brilliant  stars  in  the  form  of  a  long  square  or 
parallelogram,  intersected -in  the  middle  by  the  "Three  Stars," 
or  "  Ell  and  Yard,"  about  25°  S.  of  the  Bull's  horns,  form  the 
outlines  of  Orion.     The  two  upper  stars  in  the  parallelogram  are 
about  15°  N.  of  the  two  lower  ones  ;  and,  being  placed  on  each 
shoulder,  may  be  called  the  epaulets  of  Orion.     The  brightest 
of  the  two  lower  ones  is  in  the  left  foot,  on  the  W.,  and  the 
other  which  is  the  least  brilliant  of  the  four,  in  the  right  knee. 
To  be  more  particular  ;  Bellatrix  is  a  star  of  the  2d  magnitude 
on  the  W.  shoulder  ;  Betelguese  is  a  star  of  the  1st  magnitude, 
7|°  E.  of  Bellatrix,  o-i  the  E.  shoulder.     It  is  brighter  than 
Bellatrix,  and  lies  a  little  farther  toward  the  north  ;  and  comes 
to  the  meridian  30  minutes  after  it,  on  the  21st  of  January. 
These  two  form  the  upper  end  of  the  parallelogram. 

73.  Rigd  is  a  splended  star  of  the  1st  magnitude,  in  the  left 
foot,  on  the  W.  and  15°  S.  of  Bellatrix.     8aiph  is  a  star  of  the 
3d  magnitude,  in  the  right  knee,  8£°  E.  of  Rigel.     These  two 
form  the  lower  end  of  the  parallelogram. 

uented  on  the  maps:  ?  How  described  by  Manilius  ?  71.  Situation  of  Orion?  Number 
of  visible  stars  ?  Magnitudes?  72.  What  is  the  Ell  and  Yard?  What  constitutes  the 
outline  of  Orion?  Where  is  BeUatrixt  £ctelgue«e  and  magnitude?  73.  Rigel\ 
Haipht 


ORION.  43 


"  First  in  rank 

The  martial  star  upon  his  shoulder  flames ; 
A  rival  star  illuminates  his  foot ; 
And  on  his  girdle  beams  a  luminary 
Which,  in  vicinity  of  other  stars, 
Might  claim  the  proudest  honors." 

74.  There  is  a  little  triangle  of  three  small  stars  in  the  head 
of  Orion,  which  forms  a  larger  triangle  with  the  two  in  his 
shoulders.     In  the  middle  of  the  parallelogram  are  three  stars 
of  the  2d  magnitude,  in  the  belt  of  Orion,  that  form  a  straight 
line  about  3°  in  length  from  N.  W.  to  S.  E.     They  are  usually 
distinguished  by  the  name  of  the  Three  Stars,  because  there  are 
DO  other  stars  in  the  heavens  that  exactly  resemble  them  in 
position  and  brightness.     They  are  sometimes  denominated  the 
Three  Kings,  because  they  point  out  the  Hyades  and  Pleiades 
on  one  side,  and  Sirius,  or  the  Dog-star,  on  the  other.     In  Job 
they  are  called  the  Bands  of  Orion  ;  while  the  ancient  husband- 
men called  them  Jacob's  rod,  and   sometimes  the  Rake.     The 
University  of  Leipsic,  in  1807,  gave  them  the  name  of  Napoleon. 
But   the   more  common  appellation  for  them,    including  those 
in  the  sword,  is  the  Ell  and  Yard.     They  derive  the  latter  name 
from  the  circumstance  that  the  line  which  unites  the  "  three 
stars"  in  the  belt  measures  just  3°  in  length,  and  is  divided  by 
the  central  star  into  two  equal  parts,  like  a  yard-stick  ;  thus 
serving  as  a  graduated  standard  for  measuring  the  distances  of 
stars  from  each  other.     When,  therefore,  any  star  is  described 
as  being  so  many  degrees  from  another,  in  order  to  determine 
the  distance,  it  is  recommended  to  apply  this  rule. 

It  is  necessary  that  the  scholar  should  task  his  ingenuity  only  a  few  evenings  in  apply- 
ing such  a  standard  to  the  stars,  before  he  will  learn  to  judge  of  their  relative  distance* 
with  an  accuracy  that  will  seldom  vary  a  degree  from  the  truth. 

75.  The  northernmost  star  in  the  belt,  called  Mintika,  is  less 
than  y  S.  of   the  equinoctial,  and  when  on  the  meridian,  is 
almost  exactly  over  the  equator.     It  is  on  the  meridian,  the  24th 
of  January.     The  "three  stars"  are  situated  about  8°  W.  of 
the  solstitial  colure,  and  uniformly  pass  the  meridian  one  hour 
and  fifty  minutes  after  the  seven  stars.     There  is  a  row  of  stars 
of  the  4th  and  5th  magnitudes,  S.  of  the  belt,  running  down 
obliquely  towards  Saiph,  which  forms  the  sword.     This  row  is 
also  called  the  Ell  because  it  is  once  and  a  quarter  the  length 
of  the  Yard  or  belt. 

74.  What  constitutes  the  head  of  Orion?  What  in  the  middle  of  the  parallelogram f 
Names,  and  why?  "Three  stars?"  "Three  Kings?"  "Bands  of  Orion,"  "Jacob's 
Rod,"  Napoleon,"  "  Ell  and  Yard  ?  Use  of  the  Ell  and  Yard  ?  75.  What  said  of  Mivt, 
tikat  Of  the  "three  stars?"  What  other  row  of  stars ?  Forms  what?  Called  wb*t 
and  why  ? 


44  ASTRONOMY. 

T6.  About  9°  W.  of  Bellatrix,  are  eight  stars,  chiefly  of  the 
4th  magnitude,  in  a  curved  line  running  N.  and  S.  with  the  con- 
cavity toward  Orion ;  these  point  out  the  skin  of  the  lion  in 
his  left  hand.  Of  Orion,  on  the  whole,  we  may  remark  witb 
Eudosia: — 

"  He  who  admires  not,  to  the  stars  is  blind." 

HISTORY. 

According  to  some  authorities,  Orion  was  the  son  of  Neptune  and  queen  Euryale,  a 
famous  Amazonian  huntress,  and  possessing  the  disposition  of  his  mother,  he  became 
the  greatest  hunter  in  the  world,  and  even  boasted  that  there  was  not  an  animal  on 
ea.-th  which  he  could  not  conquer.  To  punish  this  vanity,  it  is  said  that  a  scorpion 
sprung  up  out  of  the  earth  and  bit  his  foot,  that  he  died  ;  and  that  at  the  request  of 
Diana  he  was  placed  among  the  stars  directly  opposite  to  the  Scorpion  that  caused  his 
death.  Others  say  that  Orion  had  no  mother,  but  was  the  gift  of  the  gods,  Jupiter, 
Neptune,  and  Mercury,  to  a  peasant  of  Bceotia,  as  a  reward  of  piety,  and  that  he  was 
invested  with  the  power  of  walking  over  the  sea  without  wetting  his  feet.  In  strength 
and  stature  he  surpassed  all  other  mortals.  He  was  skilled  in  the  working  of  iron,  from 
which  he  fabricated  a  subterranean  palace  for  Vulcan  ;  he  also  walled  in  the  coasts  of 
Sicily  against  the  inundations  of  the  sea,  and  built  thereon  a  temple  to  its  gods. 

Orion  was  betrothed  to  the  daughter  of  (Enopion,  but  he,  unwilling  to,  give  up  his 
daughter,  contrived  to  intoxicate  the  illustrious  hero  and  put  out  his  eyes,  on  the  sea- 
shore where  he  had  laid  himself  down  to  sleep.  Orion,  finding  himself  blind  when  he 
awoke,  was  conducted  by  the  sound  to  a  neighboring  forge,  where  he  placed  one  of  the 
workmen  on  his  back,  and,  by  his  directions,  went  to  a  place  where  the  rising  sun  was 
seen  with  the  greatest  advantage.  Here  he  turned  his  face  toward  the  luminary,  and, 
as  it  is  reported,  immediately  recovered  his  sight,  and  hastened  to  punish  the  perfidioiu 
cruelty  of  CEnopion. 

As  the  constellation  Orion,  which  rises  at  noon  about  the  9th  day  of  March,  and  sets  at 
noon  about  the  21st  of  June,  is  generally  supposed  to  be  accompanied,  at  its  rising,  with 
great  rains  and  storms,  it  became  extremely  terrible  to  mariners,  in  the  early  advtm- 
tures  of  navigation.  Virgil,  Ovid,  and  Horace,  with  some  of  the  Greek  poets,  make 
mention  of  this. 

Thus  Eneas  accounts  for  the  storm  which  cast  him  on  the  African  coast  on  his  way  to 
Italy  :— 

"  To  that  blest  shore  we  steer'd  our  destined  way, 
When  sudden,  dire  Orion  rous'd  the  sea  ; 
All  charg'd  with  tempests  rose  the  baleful  star, 
And  on  our  navy  pour'd  his  wat'ry  war." 

To  induce  him  to  delay  his  departure,  Dido's  sister  advises  her  to 
"Tell  him,  that,  charged  with  deluges  of  rain, 
Orion  rages  on  the  wintry  main." 

The  name  of  this  constellation  is  mentioned  in  the  books  of  Job  and  Amos,  and  in 
Homer.  The  inspired  prophet,  penetrated  like  the  psalmist  of  Israel  with  the  omni- 
science and  power  displayed  in  the  celestial  glories,  utters  this  sublime  injunction :  "  Seek 
Him  that  maketh  the  seven  stars  and  Orion,  and  turneth  the  shadow  of  death  into 
morning."  Job  also,  with  profound  veneration,  adores  his  awful  majesty  who  "  com- 
mandeth  the  sun  and  sealeth  up  the  stare  ;  who  alone  spreadeth  out  the  heavens,  and 
maketh  Arcturus,  Orion,  and  Pleiades, and  the  chambers  of  the  south:"  and  in  anothe- 
{ilace,  the  Almighty  demands  of  him — "  Knowest  thou  the  ordinances  of  heaven?  Canst 
thou  bind  the  sweet  influences  of  the  Pleiades,  or  loose  the  bands  of  Orion ;  canst  thou 
bring  forth  Mazzaroth  in  his  season,  or  canst  thou  guide  Arcturus  with  his  sons?" 

Calmet  supposes  that  Mazzaroth  is  here  put  for  the  whole  order  of  celestial  bodies  Jr 
the  Zodiac,  which,  by  their  appointed  revolutions,  produce  the  various  seasons  of  th< 
year,  and  the  regular  succession  of  day  and  night.  Arcturus  is  the  name  of  the  prin- 
cipal star  in  Bootes,  and  is  here  put  for  the  constellation  itself.  The  expression,  his  sons, 
doubtless  refers  to  Asterion  and  Chara,  the  two  greyhounds,  with  which  he  sterns  to  be 
pursuing  the  Great  Bear  around  the  North  pole. 

76.  What  star?  mentioned  west  of  Bellatrix?    Remark  respecting  Orion? 

HISTORY. — Story  of  parentage?  Disposition  and  boasting?  Punishment?  Wha( 
ether  account?  What  mention  of  by  Virgil?  By  Job  and  Homer?  Supposition  of 
Calmet?  Wha'  meant  by  "Arcturus  and  his  sons?" 


LEPU8.  45 

TELESCOPIC  OBJECTS. 

1.  a  ORIONIS  (Betdguese)—^..  A.  5h.  46m.  80s. ;  Dec.  N.  7*  22'  3*.    A  1,  orange  tint; 
B  11,  bluish. 

2.  /3  ORIONIS  (RigeD— R.  A.  5h.  6m.  51s  ;  Dec.  S.  8°  23'  5'.    A  1,  pale  yellow;   B  9, 
sapphire  blue.     Map  VIII.  Fig.  3. 

3.  y  OKIONIS  (JBellatrix)—l{.  A.  5h.  16m.  33s. ;   Dec.  N.  6°  12'.    A  FINK  STAR,  with  a 
minute  d'stant  companion.    A  2,  pale  yellow  ;  13  15,  grey. 

4.  6  ORIOXIS  (Mintafai) — A  coarse  DOUBLE  STAR  in  the  girdle  of  the  figure;  R.  A.  5h 
23ru.  50s. ;  Dec.  S.  0°  25'  4".     A  2,  white ;  B  7,  pale  violet. 

5.  e  ORIONIS  (Alnilam)  in  the  centre  of  his  belt ;  R.  A.  5h.  28m.  06s. ;  Dec.  S.  1*  18'  C* 
A  2^,  white  and  nebulous;  B.  10,  pale  blue. 

6.  C  OKIONIS  (Alnitali)  the  last  or  lowest  in  the  belt;  R.  A.  5h.82m.  41s.;  Dec.  3.  2°  O^. 
A  fine  TRIPLE  STAR.     A  3,  topaz  yellow ;  B  6}£,  light  purple ;  and  C  10,  gray. 

7.  A  minute  DOUBLE  STAR  and  cluster,  in  Orion's  left  hand;  R.  A.  5h.  59m.  25s. ;  Dec. 
N.  13°  58'  6\    A  7>$,  B  8}$,  both  lucid  white. 

8.  Another  DOCBLE  STAR  in  a  cluster,  in  the  left  shoulder;  R.  A.  6h.  03m.  35s. ;  Dec.  N. 
5*  28' 9".    A  9)6  and  B  10,  both  pale  yellow.    A  tolerably  rich  cluster,  with  numerous 
stragglers. 

9.  A  PLANKTAT  NEBULA,  of  a  bluish  white  tint,  on  the  nape  of  Orion's  neck — small,  pale, 
but  quite  distinct.     R.  A.  5h.  33m.  21s. ;  Dec.  N.  9°  00'  2". 

10.  Two  stars  "  in  a  WISPY  NEBULA,"  just  above  the  left  hip;  R.  A.  5h.  3Sm.  33s.;  Dec. 
N.  0°  00'  7".     A  8^  and  B.  9,  both  white.  A  singular  mass,  between  two  small  stars,  about 
equi-distant,  in  a  blankish  part  of  the  heavens. 

11.  The  GREAT  NEBULA  OF  ORION — The  most  conspicuous  nebula  in  all  the  heavens.    It 
is  situated  in  the  bword  of  Orion,  below  the  middle  star  of  the  belt ;  R.  A.  5h.  27m.  25s.; 
Dec.  S.  5°  30'.     For  its  position  in  the  constellation  see  Map  VIII.,  Fig.  31.     It  maj-  be 
seen  with  a  common  telescope.     There  is  an  apparent  opening  in  one  side  of  this  nebula, 
through  which,  as  through  a  window,  we  seetu  to  get  a  glimpse  of  other  heavens,  and 
brighter  regions.    (Map  VIII.,  Fig.  82.) 

12.  The  middle  star  in  the  sword  is  in  the  midst  of  this  nebula,  and  with  powerful  tele- 
scopes is   found  to  be  sextuple.     The  writer  has  often  seen  the  fifth  star  with  a  6-inch 
refractor.    These  stars  constitute  the    Trapezium  of  Orion.    The  region  around   this 
nebula  is  rich  in  stars,  as  shown  on  Map  Vill.,  Fig.  33. 


LEPUS  (THE  HAKE).— MAP  III. 

77.  This  constellation  is  situated  directly  south  of  Orion,  and 
comes  to  the  meridian  at  the  same  time  ;  namely,  on  the  24th 
of  January.     It  has  a  mean  declination  18°  S.,  and  contains  19 
fciuull  stars,  of  which,  the  four  principal  ones  are  of  the  3d  magni- 
tude.    It  may  be  readily  distinguished  by  means  of  four  stars 
of  the  3d  magnitude,   in  the  form  of  an  irregular  square,  or 
trapezium. 

78.  Zeto,  of  the  4th  magnitude,  is   the   first  star,  and  is 
situated  in  the  back,  5°  S  of  Saiph*,  in  Orion.     About  the  same 
distance  below  Zeta  are  the  four  principal  stars,  in  the  legs  and 
feet.     These  form  the  square.     They  are  marked  Alpha,  Beta, 
Gamma,,  Delta. 

TELESCOPIC  OBJECTS.— Alpha ?  Beta?  Gamma?  Delta,  &c.l  What  double  BtaisT 
Nebula?  ?  Point  out  on  the  map  ? 

77.  Location  of  Lepus?  Number  and  magnitude  of  stars?  How  may  it  be  distiu- 
puished?  78.  Size  and  situation  of  Zeta?  Other  principal  stars?  How  marked  oa 
the  map  f 


46  ASTRONOiMY. 

•f. 

79.  Alpha,  otherwise  called  Arneb,  and  Beta  form  the  N.  W. 
end  of  the  trapezium,  and  are  about  3°  apart.  Gamma  and 
Delta  form  the  S.  E.  end,  and  are  about  2£°  apart.  The  upper 
right-hand  one,  which  is  Arneb,  is  the  brightest  of  the  four,  and 
is  near  the  centre  of  the  constellation.  Four  or  five  degrees  S. 
of  Iligel  are  four  very  minute  stars,  in  the  ears  of  the  Hare. 

HISTORY. 

This  constellation  is  situated  about  18°  west  of  the  Great  Dog,  which,  from  the  motion 
of  tin  earth,  seetr.s  to  be  pursuing  it,  as  the  Greyhounds  do  the  Bear,  round  the  Circuit 
of  the  skies  It  was  one  of  those  animals  which  Orion  is  said  to  have  delighted  in  hunt- 
ing, and  which,  tor  this  reason,  was  made  into  a  constellation  and  placed  near  hire 
among  the  stars. 

TELESCOPIC  OBJECTS. 

1.  a  LKPORIS  (Arneb')— A  distant  DOUBLE  STAR  ;  R.  A.  5h.  25m.  40s. ;  Dec.  S.  17°  56'  05*. 
A  33$,  pale  yellow  ;  B  9>£,  grey. 

2.  $  LKPORIS  (Nihal) — A  STAR  with  a  distant  telescopic  companion ;  R.  A.  5h.  21m.  23s. ; 
Dec.  S.  20'  W  05".    A  4,  deep  yellow;  B  11,  blue. 

3.  y  LKPOH.&— A  wide  TRIPLE  STAR  in  a  barren  field;  R.  A.  5h.  3Tm.  48s.;  Dec.  S.  22" 
80'  0'2'.     .A  *,  light  yellow  ;  B  6^,  pale  green  ;  C  13,  dusky. 

4.  L  LEPORIS— A  delicate  DOCBLK  STAR  in  the  Hare's  left  ear ;  R.  A.  5h.  04m.  50s. ;  Dec. 
S.  12*  03'  09".     A  4%,  white ;  B  12,  pale  violet,  with  a  reddish  distant  star  nearly  north. 

5.  K  LEPORIS — A  close  DOUBLE  STAR,  at  the  root  oilhe  left  ear;  R.  A.  5h.  5in.  51s. ;  Dec. 
B.  13"  08'.    A  5,  pale  white ;  B  9,  clear  grey. 

6.  A  bright  STELLAR  NEBCLA,  under  the  Hare's  feet;  R.  A.  5h.  17m.  50s. ;  Dec.  S.  24*  39' 
09".     A  fine  object  of  a  milky  white  tinge,  and  blazing  towards  the  centre.     Hersche^ 
describes  it  as  "  a  beautiful  cluster  of  stars,  nearly  3'  in  diameter,  of  a  globular  forn\ 
and  extremly  rich."    An  imaginary  Jine  run  from  Betelguese  before  a  Leporis,  and  o/etf 
S,  will  hit  this  object  about  4°  south-west  of  the  latter. 


COLUMBA  (NOAH'S  DOVE).— MAP  III. 

80.  This  constellation  is  situated  about  16°  S.  of  tho  Hare, 
and  is  nearly  on  the  same  meridian  with  the  "  Three  Stors,"  in 
the  belt  of  Orion.  It  contains  only  10  stars  ;  one  of  the  2d, 
one  of  the  3d,  and  two  of  the  4th  magnitudes  ;  of  these  Phaet 
and  Beta  are  the  brightest,  and  are  about  2£°  apart.  Phaet, 
the  principal  star,  lies  on  the  right,  and  is  the  highest  of  the 
two  ;  Beta  may  be  known  by  means  of  a  smaller  star  just  east 
of  it,  marked  Gamma.  A  line  drawn  from  the  easternmost  star 
in  the  belt  of  Orion,  32°  directly  south,  will  point  out  Phaet  ;  it, 
is  also  11^-°  S.  of  the  lower  left-hand  star  in  the  square  of  the 
Hare,  and  makes  with  Sirius  and  Naos,  in  the  ship,  a  large  equi- 
lateral triangle. 

79.  What  other  name  has  Alpha ;  and  with  Beta  what  does  it  form  ?    What  further 
description  ? 

HISTORY.— Why  was  Lepus  placed  in  the  heavens? 

TELESCOPIC  OBJECTS.— Alpha ?    Beta?     Gamma?    Iota?    Kappa?    Nebula? 

80.  Situaticn  of  Columba?     Number  and  size  of  stars?     The  two  brightest,  and  situa- 
tion ?    How  find  Pha«t  ?     What  figure  does  it  help  to  form  ?    With  what  other  stars  ? 


ERIDANUS.  47 


HISTORY. 

This  constellation  is  so  called  in  commemoration  of  the  dove  wh  ch  Noah  "  seat  forth 
to  sec  if  the  waters  were  abated  from  off  the  face  of  the  groun.l,"  after  (he  ark  had 
rested  on  mount  Ararat.  "  And  the  dove  came  in  to  him  in  the  evening,  and  lo,  in  her 
mouth  was  an  olive  leaf  plucked  off. 


1  The  surer  messenger, 


A  dove  sent  forth  once  and  again  to  spy 
Green  tree  or  ground,  whereon  his  foot  may  light : 
The  second  time  returning  in  his  bill 
An  olive  leaf  ho  brings,  pacific  sign  1" 


ERTDANUS  (THE  RIVER  PO).— MAP  III. 

81.  This  constellation  meanders  over  a  large  and  very  irregu- 
lar space  in  the  heavens.     It  is  not  easy,  nor  scarcely  desirable, 
to  trace  oat  all  its  windings  among  the  stars.     Its  entire  length 
is  riot  less  than  130°  ;  which,  for  the  sake  of  a  more  easy  refer- 
ence, astronomers  divide  into  two  sections,  the  northern   and 
the  southern.     That  part  of  it  which  lies  between  Orion  and  the 
Whale,  including  the  great  bend  about  his  paws,  is  distinguished 
by  the   name  of  the  Northern  stream;  the  remainder  of  it  is 
called  thv3  Southern  stream. 

82.  The  Northern  stream  commences  near  Rigel,  in  the  foot  of 
Orion,  and  flows  out  westerly,  in  a  serpentine  course  nearly  40° 
to  the  Whale,  where  it  suddenly  makes  a  complete  circuit,  and 
returns  back  nearly  the  same  distance  towards  its  source,  but 
bending  gradually  down  toward  the  south,  when  it  again  makes 
a  similar  circuit  to  the  S.  W.,  and  finally  disappears  below  the 
horizon. 

West  of  Rigel  th*rf-e  are  five  or  six  stars  of  the  3d  and  4th  magnitudes,  arching  up  in  a 
femi-circular  form,  a-»d  marking  the  Jimi  bend  of  the  northern  stream.  About  8"  below 
these,  or  19°  W.  of  ll.pel,  is  a  bright  star  of  the  2d  magnitude,  in  the  second  bend  of  the 
northern  stream,  marked  Gamma.  This  star  culminates  la  minutes  after  the  Pleiades, 
and  one  hour  and  a  quarter  before  Rigel.  Passing  Gamma,  and  a  smaller  star  west  of 
it,  there  are  four  stars  nearly  in  a  row,  which  bring  us  to  the  breast  of  ('--tus.  8°  N.  of 
Garnma,  is  a  small  stai  named  Kied>  which  is  thought  by  some  to  be  considerably  ne»ivr 
the  earth  than  Sinus. 

Tlieemim,  in  the  southern  stream,  is  a  star  of  the  3d  magnitude,  about  17*  S.  W.  of 
the  square  in  Lepus,  ami  may  be  known  by  means  of  a  smaller  star  1°  above  it.  Acker- 
n((r  is  a  brilliant  star  of  the  1st  magnitude,  in  the  extremity  of  the  southern  stream; 
but  having  53°  of  S.  declination,  can  never  be  seen  in  this  latitude. 

83.  The  whole  number  of  stars  in  this  constellation  is  84  ;  of 
which,  one  is  of  the  1st  magnitude,  one  of  the  2d,  and  eleven 
are  of  the  3d      Many  of  these  cannot  be  pointed  out  by  verbal 
description  ;  they  must  be  traced  from  the  map. 

HISTORY  — Origin  of  this  constellation  ? 

81.  What  said  of  Eridauus?  Length?  How  divided?  82.  Trace  the  Northern 
•Ureain?  Gamma?  Theemim?  Achernar?  88.  Whole  number  of  stars  in  Eridauo*  ? 


48  ASTRONOMY. 

84.  In  the  upper  part  of  the  Northern  stream,  near  the  feet 
of  Taurus,  nay  be  seen  a  modern,  but  now  discarded  constella- 
tion, of  which  Captain  Smyth  says:  "Abbe  Hell  (who  also 
placed  Herschel's  Telescope  among  the  celestials)  has  squeezed 
in  his  Harpa  Georgii,  to  compliment  a  sovereign  of  those  realms  ; 
having  niched  from  Eridanus  about  thirty  or  forty  stars,  some 
of  the  4th  magnitude,  for  the  purpose. 

HISTORY. 

Eridanus  is  the  name  of  a  celebrated  river  in  Cisalpine  Gaul,  also  called  Padus.  Itrf 
modern  name  is  Po.  Virgil  calls  it  the  king  of  rivers.  The  Latin  poets  have  rendered 
it  memorable  from  its  connection  with  the  fable  of  Phaeton,  who,  being  a  son  of  Phoebus 
and  Clymene,  became  a  favorite  of  Venus,  who  intrusted  him  with  the  care  of  one  of 
her  temples.  This  favor  of  the  goddess  made  him  vain,  and  he  sought  of  his  father  a 
public  and  incontestable  sign  of  his  tenderness,  that  should  convince  the  world  of  his 
origin.  Phoebus,  after  some  hesitation,  made  oath  that  he  would  grant  him  whatever 
be  required,  and  ao  sooner  was  the  oath  uttered,  than  — 

"  The  youth,  transported,  asks  without  delay, 

To  guide  the  sun's  bright  chariot  for  a  day. 

The  god  repented  of  the  oath  he  took, 

For  anguish  thrice  his  radiant  head  he  shook;— 

My  son,  says  he,  some  other  proof  require, 

Rash  was  my  promise,  rash  was  thy  desire  — 

Not  Jove  himself,  the  ruler  of  the  sky, 

That  hurls  the  three-forked  thunder  from  above, 

Dares  try  his  strength  ;  yet  who  as  strong  as  Jove? 

Besides,  consider  what  impetuous  force 

Turns  stars  aud  planets  in  a  diflti  rent  course. 

I  steer  against  their  motions  ;  nor  am  I 

Borne  buck  by  all  the  current  of  the  sky: 

But  how  could  you  resist  the  orbs  that  roll 

In  adverse  whirls,  anJ  stem  the  rapid  po'e?" 

Phoebus  represented  the  dangers  to  which  he  would  be  exposed  in  vain.  He  under- 
took the  afirial  journey,  and  the  explicit  directions  of  his  father  were  forgotten.  No 
sooner  had  Phaeton  received  the  reins  than  he  betrayed  his  ignorance  of  the  manner 
of  guiding  the  chariot.  The  flying  coursers  became  sensible  of  the  confusion  of  their 
driver,  and  immediately  departed  from  the  usual  track.  Phaeton  repented  too  late  of 
his  rashness,  and  already  heaven  and  earth  were  threatened  with  a  universal  confla- 
gration as  the  consequence,  when  Jupiter,  perceiving  the  disorder  of  the  horses,  struck 
the  driver  with  a  thunderbolt,  and  hurled  him  headlong  from  heaven  into  the  rivet 
Eridanus.  His  body,  consumed  with  fire,  was  found  by  the  nymphs  of  the  place,  wh» 
honored  him  with  a  decent  burial,  and  inscribed  this  epitaph  upon  his  tomb:  — 
ulf>£  situs  e&t  Phaeton^  currus  auriga  pnterni  .' 

Queue  si  non  tenuit,  magnits  tamen  excidit  ausi*." 

His  sisters  mourned  his  unhappy  end,  and  were  changed  by  Jupiter  into  poplars. 
"All  the  long  night  their  mournful  watch  they  keep, 

And  all  the  day  stand  round  the  tomb  and  weep."  —  OVID. 

It  is  said  the  tears  which  they  shed  turned  to  amber,  with  which  the  Phoenicians 
and  Carthaginians  carried  on  in  secrecy  a  most  lucrative  trade.  The  great  heat  pro- 
duced on  the  occasion  of  the  sun's  departing  out  of  his  usual  course,  is  said  to  have 
dried  up  the  blood  of  the  Ethiopians,  and  turned  their  skins  black;  and  to  have  pro- 
duced sterility  and  barrenness  over  the  greater  part  of  Libya. 

"At  once  from  life  and  from  the  chariot  driven, 
Th*  ambitious  boy  fell  thunderstruck  from  heaven.** 

W.  What  discarded  constellation  mentioned?  Is  it  on  the  mapT  Remark  of  Capt. 
Bmyth? 

.—  Named  after  what?     Modern  name?     Fable  of  Phaeton?     Its  evidcn* 


allusion:- 


AURIGA.  49 

**The  breathless  Phaeton,  with  flaming  hah, 
Shot  from  the  chariot  like  a  falling  star, 
That  in  a  summer's  evening  from  the  top 
Of  heaven  drops  down,  or  seems  at  least  to  drop, 
Till  on  the  Po  his  blasted  corpse  was  hurl'd, 
Far  from  his  country,  in  the  western  world." 

The  fable  of  Phaeton  evidently  alludes  to  some  extraordinary  heats  which  wer« 
exoerienced  in  a  very  remote  period,  and  of  which  only  thia  confused  tradition  hai 
defended  to  later  times. 

TELESCOPIC    OBJECTS. 

1.  /?  ERIDANT — A  bright  star  with  a  distant  telescopic  companion,  on  the  shin  bone  of 
Orion ;  R.  A.  4h.  59m.  59s. ;  Dec.  S.  5°  17'  9'.    A  3,  topaz  yellow ;  B  12,  pale  blue.    TLi* 
star  is  just  above  Rigel,  in  the  direction  of  the  Hyades. 

2.  y  EHIDANI — A  star  with  a  distant  companion ;   R.  A.  3h.  50m.  34s. ;    Dec.  S.  13*  5S'. 
A  2J$,  yellow;  B  10  pale  grey. 

8.  A  MILK  WHITE  NEBULA  ;  R.  A.  3h.  33m.  02s. ;  Dec.  S.  19*  04'  8*.  Pale,  distinct,  round, 
and  bright  in  the  centre. 

4.  A  PLANETARY  NEBULA;  R.  A.  4h.  06m.  50s. ;  Dec.  S.  13*  09'  1*.  About  4%"  from  y 
in  the  direction  of  Kigel.  A  splendid  though  not  very  conspicuous  object,  of  a  greyish 
white  color.  Map  VIII.,  Fig.  34,  represents  it  in  its  best  aspects,  highly  magnified, 
with  four  telescopic  stars  in  the  field,  two  of  which  point  exactly  towards  the  nebula. 


SCEPTRUM  BRANDEKBURGITJM  (SCEPTEB  OF  BRANDENBURG). 
MAP  III. 

85.  This  is  a  slender  constellation,  situated  between  the  two 
streams  of  theHiver  Po.  It  was  constructed  by  Kirch,  in  1688, 
and  recognized  by  Bode  a  century  afterwards;  but  is  now  gene- 
rally discarded,  though  retained  on  the  map.  It  is  composed  of 
four  stars  of  the  3d,  4th  and  5th  magnitudes,  running  north  anfl 
south;  and  is  usually  included  in  Eridanus. 


AURIGA  (THE  CHARIOTEER). — MAP  III. 

86.  The  Charioteer,  called  also  the  Wagoner,  is  represented 
on  the  celestial  map  by  the  figure  of  a  man  in  a  reclining  posture, 
resting  one  foot  upon  the  horn  of  Taurus,  with  a  goat  and  her 
kids  in  his  left  hand,  and  a  bridle  in  his  right. 

It  is  situated  N.  of  Taurus  and  Orion,  between  Perseus  on 
the  W.  and  the  Lynx  on  the  E.  Its  mean  declination  is  45° 
N. ;  so  that  when  on  the  meridian,  it  is  almost  directly  overhead 
in  New  England.  It  is  on  the  same  meridian  with  Orion,  and 
culminates  at  the  same  hour  of  the  night.  Both  of  these  con- 
stellations are  on  the  meridian  at  9  o'clock  on  the  24th  of 


.— Beta?     Gamma?    Nebula?    Point  out  on  the  map. 
85.  Describe  the  Sceptre  of  Brandenburgh  ?    Situation?    When  and  by  whom  consti- 
tuted?   Is  it  recognized  by  astronomers?     Number  and  magnitude  of  stars?        86.  liow 
is  Auriga  represented?    Situation?     When  on  the  meridian? 


60  ASTRONOMY. 

January,  and  1  hour  and  40  minutes  east  of  it  on  the  1st  of 
January. 

87.  The  whole  number  of  visible  stars  in  Auriga,  is  66, 
incl tiding  one  of  the  1st  and  one  of  the  2d  magnitude,  which 
mark  the  shoulders.  Capella  is  the  principal  star  in  this  con- 
stellation, and  is  one  of  the  most  brilliant  in  the  heavens.  It 
takes  its  name  from  Capella,  the  goat,  which  hangs  upon  the 
left  shoulder.  It  is  situated  in  the  west  shoulder  of  Auriga,  24° 
E.  of  Algol,  and  28°  N.  E.  of  the  Pleiades.  It  may  be  known 
by  a  little  sharp-pointed  triangle  formed  by  three  stars,  3°  or  4° 
this  side  of  it,  on  the  left.  It  is  also  18°  N.  of  El  Nath,  which 
is  common  to  the  northern  horn  of  Taurus,  and  the  right  foot 
of  Auriga.  Capella  comes  to  the  meridian  on  the  19th  of 
January,  just  2£  minutes  before  Rigel,  in  the  foot  of  Orion, 
which  it  very  much  resembles  in  brightness. 

Menkalina,  in  the  east  shoulder,  is  a  star  of  the  2d  magnitude,  7%'  E.  of  Capella,  and 
culminates  the  next  minute  after  Betelguese,  31%°  S.  of  it.  Theta,  in  the  right  arm,  is  a 
star  of  the  4th  magnitude,  8°  directly  south  of  Menkalina. 

It  may  be  remarked  as  a  curious  coincidence,  that  the  two  stars  in  the  shoulders  of 
Auriga  are  of  the  same  magnitude,  and  just  as  far  apart  as  those  in  Orioi,  and  opposite 
to  them.  Again,  the  two  stars  in  the  shoulders  of  Auriga,  with  the  two  in  the  shoulders 
of  Orion,  mark  the  extremities  of  a  long,  narrow  parallelogram,  lying  N.  and  S.,  and 
whose  length  is  just  five  times  its  breadth.  Also,  the  two  stars  in  Auriga,  and  the 
two  in  Orion,  make  two  slender  and  similar  triangles,  both  meeting  in  a  common  point, 
half  way  between  them  at  El  Nath,  in  the  northern  horn  of  Taurus. 

Dcltit,  a  star  of  the  4th  magnitude  in  the  head  of  Auriga,  is  about  9°  N.  of  the  two  in 
the  shoulders,  with  which  it  makes  a  triangle,  about  half  the  height  of  those  just  alluded 
to,  with  the  vertex  at  Delta.  The  two  stars  in  the  shoulders  are  therefore  the  base  of 
two  similar  triangles,  one  extending  about  9°  N.  to  the  head,  the  other  18°  £.  to  the  heel, 
on  Ihe  top  of  the  horn  :  both  figures  together  resembling  an  elongated  diamond. 

Delta  in  the  head,  Menkalina  in  the  right  shoulder,  and  Theta  in  the  arm  of  Auriga, 
make  a  straight  line  with  Betelguese  in  Orion,  Delta  in  the  square  of  the  Hare,  and  Beta 
In  Noah's  Dove ;  all  being  very  nearly  on  the  same  meridian,  48  W.  of  the  solstitial 
eolure. 

"  See  next  the  Goatherd  with  his  kids ;  he  shines 

With  seventy  stars,  deducting  only  four, 

Of  which  Capella  never  sets  to  us. 

And  scarce  a  star  with  equal  radiance  beams 

Upon  the  earth :  two  other  stars  are  seen 

Due  to  the  second  order." — JSudosia. 

HISTORY. 

The  Greeks  give  various  accounts  of  this  constellation ;  some  supposed  it  to  be  Erieh- 
Ihonius,  the  fourth  king  of  Athens,  and  son  of  Vulcan  and  Minerva,  who  awarded  him  a 
r.laoe  among  the  constellations  on  account  of  his  many  useful  inventions.     He  waa  o*  a 
monstrous  shape.     He  is  said  to  have  invented  chariots,  and  to  have  excelled  all  other" 
In  the  management  of  horses.    In  allusion  to  this,  Virgil  has  the  following  lines  • — 
"  Primus  Erichthonius  currus  et  quatuor  ausus 
Jungere  equos,  rapidisque  rotis  insistere  victor." 

Georgic.  Lib.  iii.  p.  118. 

M  BoUl  Erichthonius  was  the  first  who  join'd 
Four  horses  for  the  rapid  race  design'd, 
And  o'er  the  dusty  wheels  presiding  sat." — Dryden. 


87.  Number   of  stars   visible?     Mngnitndfi   and  situation  of  Capella?     How  kmywrtf 
(denkalina?     Delta  compared  wiih  Theta? 

The  first  supposition  ?    Second?    Third?    Opinion  of  Jamieson • 


CAMELOPARDALUS.  51 

Other  writers  say  that  Bootes  invented  the  chariot,  and  that  Auriga  was  the  son  of 
Mercury,  and  charioteer  to  (Enomaus,  king  of  Pisa,  and  so  experienced,  that  he  rendered 
his  horses  the  swiftest  in  all  Greece.  But  as  neither  of  these  fables  seems  to  account  for 
the  goat  and  her  kids,  it  has  been  supposed  that  they  refer  to  Amalthaea  and  her  sister 
Melissa,  who  fed  Jupiter,  during  his  infancy,  with  goat's  milk,  and  that,  as  a  reward  for 
their  kindness,  they  were  placed  in  the  heavens.  But  there  is  no  reason  assigned  for 
their  being  placed  in  the  arms  of  Auriga,  and  the  inference  is  unavoidable,  that 
mythology  is  at  fault  on  this  point. 

Jamieson  is  of  opinian  that  Auriga  is  a  mere  type  or  scientific  symbol  of  the  beautiful 
fable  of  Phaeton,  because  he  was  the  attendant  of  Phoebus  at  that  remote  period  when 
Taurus  opened  the  year. 

TELESCOPIC  OBJECTS. 

1.  a  AURIGA  (Oapella) — A  fine  star  with  two  distant  companions,  on  the  right  shoulder- 
blade  of  Auriga  ;  R.  A.  5h.  04m.  63s. ;  Dec.  N.  45"  49'  07".    A  1,  bright  white  ;  B  12,  pale 
blue ;  C  9,  grey. 

2.  {3  AURIGA  (Menkalina) — A  bright  star  in  the  left  shoulder,  with  a  distant  com- 
panion ;  R.  A.  5h.  47m.  4Ss. ;  Dec.  N.  44°  55'  3".    A  2,  yellow;  B  10 j£,  bluish. 

3.  A  RICH  CLUSTER  of  minute  staiA,  on  the  left  thigh;  R.  A.  5h.  18m.  41s. ;  Dec.  N.  85* 
44'  9"    A  singular  figure,  somewhat  like  a  cross.    Find  by  a  line  from  Rigel,  northwards 
through  (3  Tauri,  and  about  7°  beyond. 

4.  A  RESOLVABLE  NEBULA  ;  R.  A.  6l  ,  20ra.  5ls. ;  Dec.  N.  34°  06'  9'.    Situated  in  a  rich 
field  of  minute  stars. 


CAMELOPARDALUS  (THE  OAMELOPAED).— MAP  YI. 

88.  This   constellation  was   made  by  Hevelius   out   of  the 
unformed  stars  which  lay  scattered  between  Perseus,  Auriga, 
the   head  of  Ursa  Major,  and  the  Pole  star.*    It  is   situated 
directly  N.  of  Auriga  and  the  head  of  the  Lynx,  and  occupies 
nearly  all  the  space  between  these  and  the  pole.     It  contains  58 
small  stars  ;  the  five  largest  of  which  are  only  of  the  4th  mag- 
nitude. 

89.  The  principal  star  lies  in  the  thigh,  and  is  about  20°  from 
Capella,  in  a  northerly  direction.     It  marks  the  northern  boun- 
dary of  the  temperate  zone  ;  being  less  than  one  degree  S.  of 
the  Arctic  circle.     There  are  two  other  stars  of  the  4th  magni- 
tude, near   the   right  knee,  12°  N.  E.  of  the  first  mentioned. 
They  may  be  known  by  their  standing  1°  apart  and  alone. 

The  other  stars  in  this  constellation  are  too  small,  and  too  much  scattered  to  invite 
observation. 

HISTORY. 

The  Camelopard  is  so  called  from  an  animal  of  that  name,  peculiar  to  Ethiopia.  This 
animal  resembles  both  the  camel  and  the  leopard.  Its  body  is  spotted  like  that  of  tho 
leopard.  Its  neck  is  about  seven  feet  long,  its  fore  and  hind  legs  from  the  hoof  to  tue 
Beyond  joint,  are  nearly  of  the  same  length ;  but  from  the  second  joint  of  the  legs  to  the 
r/ody,  the  fore  legs  are  so  long  in  comparison  with  the  hind  ones,  that  no  person  could  si* 
upon  its  back  without  instantly  sliding  off,  as  from  a  horse  that  stood  up  on  his  hind  feet 

TELESCOPIC  OBJECTS.— Alpha ?    Beta?     Cluster?     Nebulae? 

88.  Origin  of  Camelopardalus?  Situation  and  ejctent?  Number  and  size  of  its  Ft.\rs? 
C9.  Where  is  its  prin  ;ipal  star  ?  The  next  two ?  "How  known  ? 

. — Any  mythological  story?     What  said  of  the  anim-\l? 

B.G.  3 


52  ASTRONOMY. 

TELESCOPIC  OBJECTS. 

1.  a  CAMELOPARDALI— A  neat  DOUBLE  STAR  between  the  hind  feet  of  the  animal,  half  way 
between  a  Persei  and  6  in  the  head  of  Auriga ;  R.  A.  4h.  19m.  23s. ;  Dec.  N.  53°  33  3" 
A  7J$,  white;  B  8J£,  sapphire  blue. 

2.  Another  close  DOUBLB  STAB,  between  the  hind  feet ;  B.  A.  4h.  27m.  18s. ;  Dec.  N.  63* 
09'.    A  5J$,  yellow ;  B.  73*.  pale  blue. 

8.  A  very  delicate  DOUBLE  STAR  in  the  animal's  hind  hoof;  R.  A.  4h.  44m.  28s. ;  Dec.  N 
53°  29'  3".    A  5,  white ;  B  13,  orange. 

4.  A  fine  DOUBLE  STAR  in  the  lower  part  of  the  back  of  the  neck ;  R.  A.  4h.  46m.  19s. 
Dec.  N.  79°  01'  8".    A  5%,  light  yellow  ;  B  9,  pale  blue. 

5.  A  bright  PLANETA*?  NEBULA,  of  a  bluish  white  tint,  about  60*  in  diameter,  in  the 
nind  flank  of  the  animal,  R.  A.  4h.  53m.  29s.    Dec.  N.  60°  23'  5".    A  curious  body,  in  H 
rich  field  of  small  stars. 


CHAPTER  IV. 

CONSTELLATIONS    ON   THE    MERIDIAN    IN    FEBRUARY. 

THE  LYNX.— MAPS  III.  AND  VI. 

90.  THIS  constellation,  like  that  of  the  Camelopard,  exhibits 
no  very  interesting  features  by  which  it  can  be  distinguished.     It 
contains  only  a  moderate  number  of  inferior  stars,  scattered 
over  a  large  space  N.  of  Gemini,  and  between  Auriga  and  Ursa 
Major. 

91.  The  whole  number  of  stars  in  this  constellation  is  44, 
including  only  three  that  are  So  large  as  the  3d  magnitude. 
The  largest  of  these,  near  the  mouth,  is  in  the  solstitial  colure, 
14£°  N.  of  Menkalina,  in  the  E.  shoulder  of  Auriga.     The  other 
two  principal  stars  are  in  the  brush  of  the  tail,  3£°  S.  W.  of 
another  star  of  the  same  brightness  in  the  mouth  of  the  Lesser 
Lion,  with  which  it  makes  a  small  triangle.     Its  centre  is  on 
the  meridian  at  9  o'clock  on  the  23d,  or  at  half-past  t  on  the  1st 
of  February. 

TELESCOPIC  OBJECTS. 

1.  A  close  DOUBLE  STAR,  in  the  nose  of  the  Lynx ;  R.  A.  6h.  07m.  51s. ;  Dec.  N.  59*  25'  8' 
About  30°  from  the  Pole  star,  on  a  line  toward  Sirius.    A  6,  and  B  7^,  both  white.    An 
elegant  but  difficult  object. 

2.  A  close  DOUBLE  STAR  in  the  eye  of  the  Lynx,  between  Dubhi  and  Capella;  R.  A.  6h 
38m.  57s. ;  Dec.  N.  59°  37'  6".    A  5J^,  golden  yellow ;  B  7,  purple.    A  delicate  and  pretty 
object. 

3.  A  coarse  TRIPLE  STAR  on  the  animal's  lower  jaw;  R.  A.  6h.  12m.  50s. ;  Dec.  N.  58s 
29'  7".    A.  6,  orange  tinge ;  B  13,  blue ;  and  C  9,  pale  garnet. 

4.  A  ROUND  NEBULA,  in  the  Lynx,  or  fore  paws  of  Leo  Minor ;   R.  A.  9h.  14m.  82s. 
Dec.  N.  35°  11'  9'.    It  is  pale  white,  sparkling  in  the  centre. 

TELESCOPIC  OBJECTS.— Alpha?    What  other  double  stars?    Nebula? 
90.  Describe  the  Lynx  ?    Situation?        91.  Number  and  size  of  its  stars?    Where  is  the 
Urgest  situated?    The  other  two  principal  stars? 
TKLBBOOPIC  OBJECTS.— What  double  stars T    Triple?    NebuU 


GEMINI.  53 

TELESCOPIUM  HERSCHELLII  (HEESOHEL'S  TELESCOPE).— 
MAP  III. 

92.  About  midway  between  the  body  of  the  Lynx  and  Gemini, 
may  be  seen  the  rude  figure  of  a  refracting  Telescope,  with  its 
stand.     It  was  made  out  of  a  few  unformed  stars,  by  Abbe 
Hell,  in  honor  of  Sir  William  Herschel,  but  is  now  generally 
discarded.     It  is  reta.  aed  on  the  map  more  as  a  matter  of  history 
than  to  perpetuate  it  as  a  constellation. 

GEMINI  (THE  TWINS).— MAP  III. 

93.  This  constellation  represents,  in  a  sitting  posture,  the  twin 
brothers,  Castor  and  Pollux.     It  is  the  third  sign,  but  fourth 
constellation  in  the  order  of  the  Zodiac,  and  is  situated  south  of 
the  Lynx,  between  Cancer  on  the  east,  and  Taurus  on  the  west. 

94.  The  plane  of  the  Ecliptic  passes  through  the  centre  of 
Gemini  ;  and  as  the  earth  moves  round  in  her  orbit  from  the  first 
point  of  Aries  to  the  same  point  again,  the  sun,  in  the  mean- 
time, will  appear  to  move  through  the  opposite  signs,  or  those  which 
are  situated  right  over  against  the  earth,  on  the  other  side  of  her 
orbit.    Accordingly,  if  we  could  see  the  stars  as  the  sun  appeared 
to  move  by  them,  we  should  see  it  passing  over  the  constellation 
Gemini  between  the  21st  of  June  and  the  23d  of  July;  but  we 
seldom  see  more  than  a  small  part  of  any  constellation  through 
which  the  sun  is  then  passing,  because  the  feeble  lustre  of  the 
stars  is  obscured  by  the  superior  effulgence  of  the  sun. 

"When  the  sun  is  just  entering  the  outlines  of  a  constellation  eastward,  its  eastern  limit 
may  be  seen  in  the  evening  twilight,  just  above  the  setting  sun.  So  when  the  sun  has 
arrived  at  the  eastern  limit  of  a  constellation,  the  western  part  of  it  may  be  seen  rising 
in  the  morning  twilight,  just  before  the  rising  sun.  Under  other  circumstances,  when 
the  sun  is  said  to  be  in,  or  to  enter,  a  particular  constellation,  it  is  to  be  understood  that 
that  constellation  is  not  then  visible,  but  that  those  opposite  to  it  are.  For  example : 
whatever  constellation  sets  with  the  sun  on  any  day,  it  is  plain  that  the  one  opposite  to 
it  must  be  then  rising,  and  continue  visible  through  the  night.  Also,  whatever  constel- 
lation rises  and  sets  with  the  sun  to-day,  will,  six  months  hence,  rise  at  sun-setting,  and 
set  at  sun-rising.  For  example:  the  sun  is  in  the  centre  of  Gemini  about  the  6th  of  July, 
and  must  rise  and  set  with  it  on  that  day ;  consequently,  six  months  from  that  time,  or 
about  the  4th  of  January,  it  will  rise  in  the  east,  just  when  the  sun  is  setting  in  tho 
west,  and  will  come  to  the  meridian  at  midnight;  being  then  exactly  opposite  the  sun. 
And  as  the  stars  gain  upon  the  sun  at  the  rate  of  two  hours  every  month,  it  follows  thjtf. 
the  centre  of  this  constellation  will,  on  the  17th  of  February,  come  to  the  meridian  thrco 
liours  earlier,  or  at  9  o'clock  in  the  evening. 

The  sun  is  in  the  vernal  equinox  about  the  21st  of  March,  from  whence  it  advances 

92.  What  said  of  Herschel's  Telescope?  Why  perpetuated  on  the  map?  93.  How  ia 
(Jenvlni  represented  ?  Its  order  in  the  signs,  &c.  ?  Situation  ?  94.  How  with  respect 
':.•>  t">e  Ecliptic?  What  result  from  this  fact?  What  remarks  respecting  the  sun  and 
•>'  at  filiations  ? 


54  ASTRONOMY. 

through  one  sign  or  constellation  every  succeeding  mjnth  thereafter;  and  that  eacla 
constellation  is  one  month  in  advance  of  the  sign  of  that  name:  wherefore,  reckoi 
Pisces  in  March,  Aries  in  April,  Taurus  in  May,  and  Gemini  in  June,  Ac.,  beginning  witb 
each  constellation  at  the  21st,  or  22d  of  the  month. 

95.  Gemini  contains  85  stars,  including  two  of  the  2d,  three 
of  the  3d,  and  six  of  the  4th  magnitudes.     It  is  readily  recog- 
nized by  means  of  the  two  principal  stars,  Castor  and  Pollux, 
of  the  1st  and  2d  magnitudes,  in  the  heads  of  the  Twins,  about 
4£°  apart. 

Thare  being  only  11  minutes'  difference  in  the  transit  of  these  two  stars  over  the  meri- 
Cian,  *hey  may  both  be  considered  as  culminating  at  9  o'clock  about  the  24th  of  Febru- 
ary. Castor,  in  the  head  of  Castor,  is  a  star  of  the  1st  magnitude,  4^°  N.  W.  of  Pol- 
ux,  and  is  the  northernmost  and  the  brightest  of  the  two.  Pollux  is  a  star  of  the  2d 
magnitude,  in  the  head  of  Pollux,  and  is  4%°  S.  E.  of  Castor.  This  is  one  of  the  stars 
from  which  the  moon's  distance  is  calculated  in  the  Nautical  Almanac. 

"  .Of  the  famed  Ledean  pair, 

One  most  illustrious  star  adorns  their  sign, 
And  of  the  second  order  shine  twin  lights." 

96.  The  relative  magnitude  or  brightness  of  these  stars  has 
undergone  considerable  changes  at  different  periods  ;  whence  it 
has  been  conjectured  by  various  astronomers  that  Pollux  must 
vary  from  the  1st  to  the  3d  magnitude.     But  Herschel,  who 
observed  these  stars  for  a  period  of  25  years,  ascribes  the  varia- 
tion to  Castor,  which  he  found  to  consist  of  two  stars,  very 
close  together,  the  less  revolving  about  the  larger  once  in  342 
years  and  two  months. 

Bradley  and  Maskelyne  found  that  the  line  joining  the  two  stars  which  form  Castor 
was,  at  all  times  of  the  year,  parallel  to  the  line  joining  Castor  and  Pollux  ;  and  that 
both  of  the  former  move  around  a  common  centre  between  them,  in  orbits  nearly  circu- 
lar, as  two  balls  attached  to  a  rod  would  do,  if  suspended  by  a  string  affixed  to  the  cen- 
tre of  gravity  between  them. 

"  These  men,"  says  Dr.  Bowditch,  "  were  endowed  with  a  sharpness  of  vision,  and  a 
power  of  penetrating  into  space,  almost  unexampled  in  the  history  of  astronomy." 

97.  About  20°  S.  W.  of  Castor  and  Pollux,  and  in  a  line 
nearly  parallel  with  them,  is  a  row  of  stars  3°  or  4°  apart, 
chiefly  of  the  3d  and  4th  magnitudes,  which  distinguish  the  feet 
of  the  Twins.     The  brightest  of  these  is  Alhena,  in  Pollux's 
upper  foot ;  the  next  small  star  S.  of  it,  is  in  his  other  foot  ; 
the  two  upper  stars  in  the  line  next  above  Gamma,  mark  Cas- 
tor's feet. 

This  row  of  feet  is  nearly  two-thirds  of  the  distance  from  Pollux  to  Betelguese  in  Orion, 
and  a  line  connecting  them  will  pass  through  Alhena,  the  principal  star  in  the  feet. 
About  two  thirds  of  the  distance  from  the  two  in  the  head  to  those  in  the  feet,  and  nearly 
parallel  with  them,  there  is  another  row  of  three  stars  about  6°  apart,  which  mark  the 

knees. 

95.  Number  of  stars  in  Gemini?  Magnitudes?  How  recognize  this  constellation? 
What  said  of  the  culmination  of  Castor,  and  of  Pollux  ?  96.  Are  they  variable  ?  What 
did  Bradley  and  Maskelyne  ascertain?  Remark  of  Bowditch?  97.  What  constitute 
Gemini  ?  Alheua  ?  How  situated  ?  What  mark  the  kneea? 


GEMINI.  55 

98.  There  are,  in  this  constellation,  two  other  remarkable 
parallel  rows,  lying  at  right  angles  with  the  former  ;  one,  lead- 
ing from  the  head  to  the  foot  of  Castor,  the  brightest  star  being 
in  the  middle,  and  in  the  knee  :  the  other,  leading  from  the 
head  to  the  foot  of  Pollux,  "the  brightest  star,  called  Wasat, 
being  in  the  body,  and  Zeta,  next  below  it,  in  the  knee. 

Wasat  is  in  the  ecliptic,  and  very  near  the  center  of  the  constellation.  The  two  stsrs, 
Mu  and  Tejat,  in  the  northern  foot,  are  also  very  near  the  ecliptic;  Tejat  is  a  small  star 
of  between  the  4th  and  5th  magnitudes,  2"  W.  of  Mu,  and  deserves  to  be  noticed  because 
it  marks  the  spot  of  the  summer  solstice,  in  the  tropic  of  Cancer,  just  where  the  sun  is  on 
the  longest  day  of  the  year,  and  is,  moreover,  the  dividing  limit  between  the  torrid  and 
the  N.  temperate  zone. 

Propus,  also  in  the  ecliptic,  2Jg°  W.  of  Tejat,  is  a  star  of  only  the  5th  magnitude,  but 
rendered  memorable  as  being  the  star  which  served  for  many  years  to  determine  the 
position  of  the  planet  Herschel,  after  its  first  discovery. 

HISTORY. 

Castor  and  Pollux  were  twin  brothers,  sons  of  Jupiter,  by  Leda,  the  wife  of  Tyndarus, 
king  of  Sparta.  The  manner  of  their  birth  was  very  singular.  They  were  educated  at 
Pallena,  and  afterwards  embarked  with  Jason  in  the  celebrated  contest  for  the  golden 
fleece,  at  Colchis;  on  which  occasion  they  behaved  with  unparalleled  courage  and 
bravery.  Pollux  distinguished  himself  by  his  achievements  in  arms  and  personal 
prowess,  and  Castor  in  equestrian  exercises  and  the  management  of  horses ;  whence  they 
are  represented,  in  the  temples  of  Greece,  on  white  horses,  armed  with  spears,  riding 
Bide  by  side,  their  heads  crowned  with  a  petasus,  on  whose  top  glitters  a  star.  Among 
the  ancients,  and  especially  among  the  Romans,  there  prevailed  a  superstition  that 
Castor  and  Pollux  often  appeared  at  the  head  of  their  armies,  and  led  on  their  troops  to 
battle  and  to  victory. 

"  Castor  and  Pollux,  first  In  martial  force, 

One  bold  on  foot,  and  one  renown'd  for  horse. 

Fair  Leda's  twins  in  time  to  stars  decreed, 

One  fought  on  foot,  one  curb'd  the  fiery  steed." — Virgil. 
*•  Castor  alert  to  tame  the  foaming  steed, 

And  Pollux  strong  to  deal  the  manly  deed." — Martial. 

The  brothers  cleared  the  Hellespont  and  the  neighboring  seas  from  pirates  after  theh 
return  from  Colchis ;  from  which  circumstance  they  have  ever  since  been  regarded  as 
the  friends  and  protectors  of  navigation.  In  the  Argonautic  expedition  during  a  violent 
storm,  it  is  said  two  flames  of  fire  were  seen  to  play  around  their  heads,  and  immediately 
the  tempest  ceased,  and  the  sea  was  calm.  From  this  circumstance,  the  sailors  inferred, 
that  whenever  both  fires  appeared  in  the  sky,  it  would  be  fair  weather ;  but  when  only 
one  appeared,  there  would  be  storms. 

St.  Paul,  after  being  wrecked  on  the  island  of  Melita,  embarked  for  Rome  "in  a  ship 
whose  sign  was  Castor  and  Pollute;"  so  formed,  no  doubt,  in  accordance  with  the  popu- 
lar belief  that  these  divinities  presided  over  the  science  and  safety  of  navigation. 

They  were  initiated  into  the  sacred  mysteries  of  Cabiri,  and  into  those  of  Ceres  at 
Eleusis.  They  were  invited  to  a  feast  at  which  Lynceus  and  Idas  were  going  to  celebrate 
their  nuptials. with  Phoebe  and  Telaria,  the  daughters  of  Leucippus,  brother  to  Tyndarus. 
They  became  enamored  of  the  daughters,  who  were  about  to  be  married,  and  resolved  to 
supplant  their  rivals :  a  battle  ensued,  in  which  Castor  killed  Lynceus,  and  was  himself 
killed  by  Idas.  Pollux  revenged  the  death  of  his  brother  by  killing  Idas ;  but  being  him- 
self immortal  and  most  tenderly  attached  to  his  deceased  brother,  he  was  unwilling  to 
survive  him;  he  therefore  entreated  Jupiter  to  restore  him  to  life,  or  to  be  deprived  him- 
self of  immortality ;  wherefore,  Jupiter  permitted  Castor,  who  had  been  slain,  tc  share 
the  immortality  of  Pollux;  and  consequently  as  long  as  the  one  was  upon  earth,  so  long 
was  the  other  detained  in  the  infernal  regions,  and  they  alternately  lived  and  died  every 
day.  Jupiter  also  further  rewarded  their  fraternal  attachment  by  changing  them  both 

98.  What  other  remarkable  rows  of  stars  in  Gemini  ?  Situation  of  Wasat  f  Of  Tejat? 
Of  ProjmsT 

HISTORY.— Myth  of  the  parentage  of  Gemini  ?  Their  achievements?  Roman  super  Hl- 
>jon  ?  That  of  sailors  ?  Allusion  of  St.  Paul  ?  Story  of  the  fatal  wedding  ? 


56  ASTRONOMY. 

into  a  constellation  under  the  name  of  Gemini,  TWVM,  which,  it  ts  strangely  pretended, 
never  appear  together,  but  when  one  rises  the  other  sets,  and  so  on,  alternately. 

"  By  turns  they  visit  this  ethereal  sky, 

And  live  alternate,  and  alternate  die." — Homer. 
M  Pollux,  cflering  his  alternate  life, 
Could  free  his  brother,  and  could  daily  go 
By  turns  aloft,  by  turns  descend  below." — Virgil. 

Castor  and  Pollux  were  worshiped  both  by  the  Greeks  and  Romans,  who  sacrificefl 
white  lambs  upon  their  altars.  In  the  Hebrew  Zodiac,  the  constellation  of  the  Twin-j 
refers  to  the  tribe  of  Benjamin. 

TELESCOPIC  OBJECTS. 

1.  a  GEMINORUM  (Castor)— A  neat  DOUBLE  STAR;  R.  A.  7h.  24m.  23s.;  Dec.  N.  82e  14'- 
A  3.  bright  white;  B  3}£,  pale  white;  with  a  third  star  of  the  llth  magnitude  about  72 
distant.    A  Binary  System,  with  a  probable  period  of  232  years.    A  beautiful  object,  and 
easily  found.    Map  VIII. ,  Fig.  4.- 

2.  ft  GEMINORUM— A  QUADRUPLE  STAR  in  the  eye  of  Pollux,  R.  A.  7h.  85m.  31s.;  Dec 
N.  28°  25'  4".    A  2,  orange  tinge ;    B  12,  ash-colored ;    C  11,  pale  violet,  with  another 
minute  companion  visible  with  the  best  instruments. 

8.  y  GEMINORUM  (Alhena)—A  coarse  TRIPLE  STAR,  in  the  right  foot  of  Pollux  i  R.  A. 
6h.  28m.  28s. ;  Dec.  N.  16°  31'  S". ;  A  3,  brilliant  white ;  B  13,  and  C  12,  both  pale  plum 
color.  It  is  on  a  line  from  Rigel  to  ft  Geminorum,  and  nearest  the  former. 

4.  J  GEMINORUM  (Wasaf) — A  DOUBLE  STAR  on  the  right  hip  of  Pollux;  R.  A.  7h.  10m. 
84s. ;  Dec.  N.  22°  16'  3'.    A  3  j£,  pale  white ;  B  9,  purple. 

5.  e  GEMINORUM  (Melucta) — A  star  with  a  distant  companion,  on  Castor's  rfght  knee  ; 
R.  A.  6h.  34m.  05s. ;  Dec.  N.  25-°  16'  9".    A  3,  white  ;  B  9>£,  cerulean  blue. 

6.  ^  GEMINORUM — A  coarse  TRIPLE  STAR  on  the  right  knee  of  Pollux ;  R.  A.  6h.  54m.  37s. ; 
Dec.  N.  20°  47'  9".     A  4,  pale  topaz ;  B  8,  violet ;  C  18,  grey. 

7.  A  CLUSTER,  near  the  right  foot  of  Castor ;  R.  A.  5h.  59m.  Ols. ;  Dec.  N.  24"  21'  8".    A 
gorgeous  field  of  stars  from  the  9th  to  the  16th  magnitudes. 

8.  A  CLUSTER  in  the  calf  of  Pollux's  right  leg;  R.  A.  6h.  45m.  56s. ;  Dec.  N.  18°  10'  5". 
A  faint  angular  group  of  extremely  small  stars,  in  a  rich  region,  but  seen  with  difficulty. 
See  Map  VIII.,  Fig.  35. 

9.  A  COMPRESSED  CLUSTER  under  the  left  shoulder  of  Pollux;   one-third  the  distance 
from  ft  Geminorum,  to  ft  Canis  Minoris ;    R.  A.  7h.  28m.  57s. ;   Dec.  N.  21°  55'  7'.     A 
faint  object  about  12  in  diameter,  with  a  small  star  near  the  centre.    Map  VHL,  Fig.  36. 


,  CANIS  MINOR  (THE  LITTLE  DOG).— MAP  III. 

99.  This  small  constellation  is  situated  about  5°  N.  of  the  equi- 
noctial, and  midway  between  Canis  Major  and  the  Twins.     It 
contains  14  stars,  of  which  two  are  very  brilliant.     The  brightest 
star  is  called  Procyon.     It  is  or*  the  1st  magnitude,  and  is  about 
4°  S.  E.  of  the  next  brightest,  marked  Gomelza,  which  is  of  the 
3d  magnitude.     These  two  stars  resemble  the  two  in  the  head 
of  the  Twins.     Procyon,  in  the  Little  Dog,  is  23°  S.  of  Pollux 
in  Gemini,  and  Gomelza  is  about  the  same  distance  S.  of  Castor. 

100.  A  great  number  of  geometrical  figures  may  be  formed 
of  the  principal  stars  in  the  vicinity  of  the  Little  Dog.     For 
example  :  Procyon  is  23°  S.  of  Pollux,  and  26°  E.  of  Betel- 

TELESCOPIC  OBJECTS.— Alpha?  Beta?  Gamma?  Delta,  Ac.?  Clusters?  Which 
Shown  on  the  map  ? 

99.  Where  is  Canis  Minor  situated?  Number  of  stars?  Name  of  brightest ?  Mag- 
litude?  Next  brightest?  What  do  these  two  resemble?  100.  What  said  of  geome- 
Tical  figures?  Of  the  name  Procyon?  Its  import? 


CANIS    MINOR.  5 

guese,  and  forms  with  them  a  large  right-angled  triangle 
Again,  Procyon  is  equi-distant  from  Betelguese  and  Sirius,  and 
forms  with  them  an  equilateral  triangle  whose  sides  are  each 
about  26°.  If  a  straight  line,  connecting  Procyon  and  Sirius, 
be  produced  23°  farther,  it  will  point  out  Phaet,  in  the  Dove. 

Procyon  is  often  taken  for  the  name  of  the  Little  Dog,  or  for  the  whole  constellation, 
c.s  Sirius  is  for  the  greater  one ;  hence  it  is  common  to  refer  to  either  of  these  constel- 
lations by  the  name  of  its  principal  star.  Procyon  comes  to  the  meridian  53  minute 
after  Sirius,  on  the  24th  of  February ;  although  it  rises,  in  this  latitude,  about  half  an 
hour  before  it.  For  this  reason,  it  was  called  Procyon^  from  two  Greek  words  which 
signify  (Ante  Canis)  "  before  the  dog." 

HISTORY. 

.The  Little  Dog,  according  to  Greek  fable,  is  one  of  Orion's  hounds.    Some  suppose  it 
refers  to  the  Egyptian  god  Anubis,  which  was  represented  with  a  dog's  head  ;  others  to 
Diana,  the  goddess  of  hunting  ;  and  others,  that  it  is  the  faithful  dog  Maera,  which 
belonged  to  Icarus,  and  discovered  to  his  daughter  Erigone  the  place  of  his  burial. 
Others,  again,  say  it  is  one  of  Actaeon's  hounds  that  devoured  their  master,  after  LMaiia 
had  transformed  him  into  a  stag,  to  prevent,  as  she  said,  his  betraying  her. 
"  This  said,  the  man  began  to  disappear 
By  slow  degrees,  and  ended  in  a  deer. 
Transform'd  at  length,  he  flies  away  in  haste, 
And  wonders  why  he  flies  so  fast 
But  as  by  chance,  within  a  neighb'ring  brook, 
He  saw  his  branching  horns,  and  alter'd  look, 
Wretched  Acteon  !  in  a  doleful  tone 
He  tried  to  speak,  but  only  gave  a  groan ; 
And  as  he  wept,  within  the  watery  glass, 
He  saw  the  big  round  drops,  with  silent  pace, 
Run  trickling  down  a  savage,  hairy  face. 
What  should  he  do  ?  or  seek  his  old  abodes, 
Or  herd  among  the  deer,  and  skulk  in  woods? 
As  he  thus  ponders,  he  behind  him  spies 
His  opening  hounds,  and  now  he  hears  their  cries. 
From  shouting  men,  and  horns,  and  dogs  he  flies. 
When  now  tlie  fleetest  of  the  pack  that  press'd 
Close  at  his  heels,  and  sprung  before  the  rest, 
Had  fastened  on  him,  straight  another  pair 
Hung  on  his  wounded  side,  and  held  him  there, 
Till  all  the  pack  came  up,  and  every  hound 
Tore  the  sad  huntsman  groveling  on  the  ground." 

It  is  not  difficult  to  deduce  the  moral  of  this  fable.  The  selfishness  and  caprice  of 
human  friendship  furnish  daily  illustrations  of  it.  While  the  good  man,  the  philanthro- 
pist, or  the  public  benefactor,  is  in  affluent  circumstances,  and,  with  a  heart  to  devise, 
has  the  power  to  minister  blessings  to  his  numerous  beneficiaries,  his  virtues  are  the 
general  theme  ;  but  when  adverse  storms  have  changed  the  ability,  though  they  could 
not  shake  the  will  of  their  benefactor,  he  is  straightway  pursued,  like  Actaeon,  by  his  own 
hounds;  and,  like  Actaeon,  he  is  "torn  to  the  ground"  by  the  fangs  that  fed  upon  his 
bounty. 

It  is  most  probable,  however,  that  the  Egyptians  were  the  inventors  of  this  con- 
otellation  ;  and  as  it  always  rises  a  little  before  the  Dog  Star,  which,  at  a  particular 
season,  they  so  much  dreaded,  it  is  properly  represented  as  a  little  watchful  crea  • 
*/ure,  giving  notice  like  a  faithful  sentinel  of  the  other's  approach. 

TELESCOPIC  OBJECTS. 

1.  a  CANIS  MINORIS  (Procyon)— A  bright  star  in  the  loins  of  the  Jog  with  a  distan 
-.ompamon  ;  R.  A.  Th.  30m.  55s  ;  Dec.  N.  5°  37'  8".  A  1  J$,  yellowish  white ;  B  8,  orango 
'int.  Several  small  stars  in  the  field. 

HISTORY.— What  is  the  Little  Dog  supposed  to  represent?    Fable  of  ActsconV     I*e 
moral  ?     Who  probably  invented  this  constellation  ?    To  represent  what? 
TELESCOPIC  OBJECTS. — Alpha  ?    Beta  ?    Double  star  ?     Triple  ? 


58  ASTRONOMY. 

2.  (3  CANTS  MINORIS  (Gomelza) — A  wide  TRIPLK  STAR  in  theneck;  R.  A.  7h.  ISm.  28s 
Dec.  N.  8°  86'  4".    A  3,  white ;  B  12,  orange ;  C  10,  flushed — the  last  coarsely  double  with 
one  of  the  same  magnitude.    Other  stars  in  the  field. 

8.  A  close  DOUBLE  STAR,  in  a  fine  vicinity  in  the  loins ;  R.  A.  7h.  81m.  37s. ;  Dec.  N.  5" 
85'  7*.    A  7,  white  ;  B  8,  ash-colored,  with  a  minute  blue  star  2'  distant. 

4.  A  WIDE  TRIPLE  STAR,  6"  S.  E.  of  Procyon  ;  R.  A.  7h.  50rn.  03s. ;  Dec.  N.  2"  38'  8".    A 
6,  pale  white ;  B  8,  bluish ;  C  9,  blue. 


MONOCEROS  (THE  UNIOOBN).— MAP  III. 

101.  This  is  a  modern  constellation,  made  out  of  the  unformed 
stars  of  the  ancients  that  lay  scattered  over  a  large  space  of 
the  heavens  between  the  two  Dogs.     It  extends  a  considerable 
distance  on  each  side  of  the  equinoctial,  and  its  centre  is  on  the 
same  meridian  with  Procyon. 

102.  It  contains  31  small  stars,  of  which  the  seven  principal 
ones  are  of  only  the  4th  magnitude.     Three  of  these  are  situ- 
ated in  the  head,  3°  or  4°  apart,  forming  a  straight  line  N.  E. 
and  S.  W.  about  9°  E.  of  Betelguese  in  Orion's  shoulder,  and 
about  the  same  distance  S.  of  Albena  in  the  foot  of  the  twins. 

The  remaining  stars  in  this  constellation  are  scattered  over  a 
large  space,  and  being  very  small,  are  unworthy  of  particular 
notice. 

HISTORY. 

The  Monoceros  5s  a  species  of  the  Unicorn  or  Rhinoceros.  It  is  about  the  size  of  a 
horse,  with  one  white  horn  growing  out  of  the  middle  of  its  forehead.  It  is  said  to  exist 
in  the  wilds  of  Ethiopia,  and  to  be  very  formidable. 

Naturalists  say  that,  when  pursued  by  the  hunters,  it  precipitates  itself  from  the 
tops  of  the  highest  rocks,  and  pitches  upon  its  horn,  which  sustains  the  whole  force  of 
its  fall,  so  that  it  receives  no  damage  thereby.  Sparmann  informs  us,  that  the  figure  of 
the  unicorn,  described  by  some  of  the  ancients,  has  been  found  delineated  on  the  surface 
of  a  rock  in  Caffraria ;  and  thence  conjectures  that  such  an  animal,  instead  of  being 
fabulous,  as  some  suppose,  did  once  actually  exist  in  Africa.  Lobo  affirms  that  he  has 
seen  it. 

The  rhinoceros,  which  is  akin  to  it,  is  found  in  Bengal,  Siam,  Cochin  China,  part  of 
China  Proper,  and  the  isles  of  Java  and  Sumatra. 

TELESCOPIC  OBJECTS. 

1.  A  most  delicate  DOUBLE  STAR  (/),  in  the  Unicorn's  eye ;  R.  A.  6h.  26m.  06s. ;  Dec.  N. 
7°  41'  05".    A  6,  yellowish  white :  B  16,  dusky.     A  difficult  object. 

2.  A  neat  DOUBLE  STAR  (&),  in  the  nostril,  7J^°  east  of  Betelguese;  R.  A.  6h.  15m.  17s. ; 
Dec.  N.  4°  40'  01".    A  5%,  golden  yellow ;  B  8,  lilac. 

3.  A  fine  TRIPLE  STAR  in  the  right  fore-leg;  R.  A.  6h.  21m.  04s.;  Dec.  S.  6*  56'  01".     A 
6J$,  white ;  B  7,  and  C  8,  both  pale  white.     A  ray  shot  from  the  Bull's  eye  through  Bella- 
trix,  and  rather  more  than  as  far  again,  will  pick  it  up.     Supposed  by  Herschel  to  be  a 
triple  system,  periods  A  B  17,000  ys.     B  C  1000.    Shown  double  only  on  the  map  of 
the  constellations.    Telescopic  view,  Map  VIII.,  Fig.  5. 

4.  A  delicate  TRIPLE  STAR,  in  a  magnificent  stellar  field,  between  the  Unicorn's  ears  ; 
R.  A.  6h.  32m.  10s. ;  Dec.  N.  10°  02'  02".     One-third  the  distance  from  Procyon  to  Alle- 
baron.    A  6,  greenish  ;  B  9%,  pale  grey ;  C  15,  blue.    A  fine  object. 

101.  Character  and  situation  of  Monoceros?  Extent?  102.  Number  and  size  of  i(.P 
stars  ?  How  three  of  the  largest  situated? 

HISTORY.— What  said  of  the  animal  itself?    Is  it  not  wholly  fabulous  ? 
TELESCOPIC  OBJECTS. — Double  stars  ?     Triple  ?    Any  shown  on  the  map  ? 


CANIS    MAJOit  59 


CANTS  MAJOR  (THE  GREAT  DOG).— MAP  El. 

103.  This  interesting  constellation  is  situated  southward  and 
eastward  of  Orion,  and  is  universally  known  by  the  brilliance 
of  its  principal  star,  Sirius,  which  is  apparently  the  largest  and 
brightest  in  the  heavens.     It  glows  in  the  winter  hemisphere  with 
a  lustre  which  is  unequaled  by  any  other  star  in  the  firmament. 
Its  distance  from  the  earth,   though  computed  at  20  millions 
of  millions  of  miles,  is  supposed  to  be  less  than  that  of  any  other 
star  :  a  distance,  however,  so  great  that  a  cannon  ball,  which 
flies  at  the  rate  of  19  miles  a  minute,  would  be  two  millions  of 
years  in  passing  over  the  mighty  interval ;  while  sound,  moving 
at  the  rate  of  13  miles  a  minute,  would  reach  Sirius  in  little  less 
than  three  millions  of  years. 

It  may  be  shown  in  the  same  manner,  that  a  ray  of  light,  which  occupies  only  8  minutes 
and  13  seconds  in  coming  to  us  from  the  sun,  which  is  at  the  rate  of  nearly  two  hundred 
thousand  miles  a  second,  would  be  3  years  and  82  days  in  passing  through  the  vast  space 
that  lies  between  Sirius  and  the  earth.  Consequently,  were  it  blotted  from  the  heavens, 
Its  light  would  continue  visible  to  us  for  a  period  of  3  years  and  82  days  after  it  had 
ceased  to  be. 

If  the  nearest  stars  give  such  astonishing  results,  what  shall  we  say  of  those  which  are 
situated  a  thousand  times  as  far  beyond  these,  as  these  are  from  us  ? 

104.  In  the  remote  ages  of  the  world,  when  every  man  was 
his  own  astronomer,  the  rising  and  setting  of  Sirius,  or  the  Dog 
Star,  as  it  is  called,  was  watched  with  deep  and  various  solici- 
tude.    The  ancient  Thebans,  who  first  cultivated  astronomy  in 
Egypt,  determined  the  length  of  the  year  by  the  number  of  its 
risings.     The  Egyptians  watched  its  rising  with  mingled  appre- 
hensions of  hope  and  fear ;  as  it  was  ominous  to  them  of  agri- 
cultural prosperity  or  blighting  drought.     It  foretold  to  them 
the  rising  of  the  Nile,  which  they  called  Siris,  and  admonished 
them  when  to  sow. 

105.  The  Romans  were  accustomed  yearly  to  sacrifice  a -dog 
to  Sirius,  to  render  him  propitious  in  his  influence  upon  their 
herds  and  fields.     The  eastern  nations  generally  believed  the 
rising  of  Sirius  would  be  productive  of  great  heat  on  the  earth. 

Thus  Virgil :— 

"  Turn  steriles  -exurere  Sirius  agros ; 

Ardebant  herbse,  et  victum  seges  segra  negabat." 


Parched  was  the  grass,  and  blighted  was  the  corn: 


Nor  'scape  the  beasts ;  for  Sirius  from  on  high, 
With  pestilential  heat  infects  the  sky.'" 


103.  Situation  of  Canis  Major?  How  known?  Supposed  distance  of  Sirius?  Illuo 
trsited  by  the  speed  of  a  cannon  ball  ?  Of  light  ?  104.  Uow  was  Sirius  regarded  by  'Jit- 
undents?  Use  made  of  it  by  the  Thebans?  The  Egyptians?  105.  Practice  of  i!i* 
Romans  ? 

O* 


60  ASTRONOMY. 

106.  Accordingly,  to  that  season  of  the  year  when  Sirius  rose 
with  the  sun  and  seemed  to  blend  its  own  influence  with  the 
heat  of  that  luminary,  the  ancients  gave  the  name  of  Dog-days, 
(Dus  canicularis.)     At  that  remote  period  the  Dog-days  com- 
menced on  the  4th  of  August,  or  four  days  after  the  summer 
solstice,  and  lasted  forty  days,  or  until  the  14th  of  September. 
At  present  the  dog-days  begin  on  the  3d  of  July,  and  continue 
to  the  llth  of  August,  being  one  day  less  than  the  ancients 
reckoned. 

107.  Hence,  it  is  plain  that  the  Dog-days  of  the  moderns 
have  no  reference  whatever  to  the  rising  of  Sirius,  or  any  other 
star,  because  the  time  of  their  rising  is  perpetually  accelerated 
by  the  precession  of  the  equinoxes  :  they  have  reference  then 
only  to  the  summer  solstice,  which  never  changes  its  position  in 
respect  to  the  seasons. 

The  time  of  Sirius'  rising  varies  with  the  latitude  of  the  place,  and  in  the  same  latitude, 
is  sensibly  changed  after  a  course  of  years,  on  account  of  the  precession  of  the  equinoxes. 
This  enables  us  to  determine  with  approximate  accuracy,  the  dates  of  many  events  of 
antiquity,  which  cannot  be  well  determined  by  other  records.  We  do  not  know,  for 
instance,  in  what  precise  period  of  the  world  Hesiod  flourished.  Yet  he  tells  us  in  his 
Opera  el  I>ies,  lib.  ii.  v.  185,  that  Arcturus  in  his  time  rose  heliacally,  60  days  after  the 
winter  solstice,  which  then  was  in  the  9th  degree  of  Aquarius,  or  39°  beyond  its  present 
position.  Now  39° :  50l£*=2794  years  since  the  time  of  Hesiod,  which  corresponds  very 
nearly  with  history. 

108.  When  a  star  rose  at  sun-setting,  or  set  at  sun-rising,  it 
was  called  the  Achronical  rising  or  setting.     When  a  planet  or 
star  appeared  above  the  horizon  just  before  the  sun,  in  the  morn- 
ing, it  was  called  the  Heliacal  rising  of  the  star  ;  and  when  it 
sunk  below  the  horizon  immediately  after  the  sun,  in  the  evening, 
it  was  called  the  Heliacal  setting. 

According  to  Ptolemy,  stars  of  the  first  magnitude  are  seen  rising  and  setting  when  the 
sun  is  12°  below  the  horizon ;  stars  of  the  2u  magnitude  require  the  sun's  depression  to 
be  13°;  stars  of  the  3d  magnitude,  14',  and  so  on,  allowing  one  degree  for  each  magni- 
tude. The  rising  and  setting  of  the  stars  described  in  this  way,  since  this  mode  of 
derfc/iption  often  occurs  in  Hesiod,  Virgil,  Columella,  Ovid,  Pliny,  &c.,  are  called  pojtwal 
rising  and  setting.  They  served  to  mark  the  times  of  religious  ceremonies,  the  seasons 
allotted  to  the  several  departments  of  husbandry,  and  the  overflowing  of  the  Nile. 

109.  The  student  may  be  perplexed  to  understand  how  the 
Dog  Star,  which  he  seldom  sees  till  mid-winter,  should  be  asso- 
ciated with  the  most  fervid  heat  of  summer.     This  is  explained 
by  considering  that  this  star,  in  summer,  is  over  our  heads  in 
the  daytime,  and  in  the  lower  hemisphere  at  night.     As  "  thick 
the  floor  of  heaven  is  inlaid  with  patines  of  bright  gold,"  by  day, 

106.  Origin  of  the  phrase  Dog-days?  When  did  they  begin  in  the  time  of  Virgil?  At 
what  time  now?  107.  What  inference  from  these  facts?  What  variation  in  the  time 
of  Sirius'  rising  ?  What  calculation  by  knowing  the  time  when  Sirius  rose,  at  any  period  V 
10S.  What  are  the  Achronical  and  Heliacal  rising  or  setting  of  a  star  or  planet?  Rr 
mark  of  Ptolemy  in  regard  to  rising  and  setting  of  the  stars  ?  109.  How  is  it  that 
Sirius  a  winter  star,  is  associated  with  iue  heat  of  summer? 


CANIS^  MAJOR.  61 

as  by  night  ;  but  on  account  of  the  superior  splendor  of  the  sun, 
we  cannot  see  them. 

110  Sirius  is  situated  nearly  S.  of  Alhena,  in  the  feet  of  the 
Twins,  and  about  as  far  S*  of  the  equinoctial  as  Alhena  is  JST. 
of  it.  It  is  about  10°  E.  of  the  Hare,  and  26°  S.  of  Betel- 

fuese  in  Orion,  with  which  it  forms  a  large  equilateral  triangle, 
t  also  forms  a  similar  triangle  with  Phaet  in  the  Dove,  and 
Naos  in  the  Ship.  These  two  triangles  being  joined  at  their 
vertex  in  Sirius,  present  the  figure  of  an  enormous  X,  called  by 
some,  the  EGYPTIAN  X.  Sirius  is  also  pointed  out  by  the  direc- 
tion of  the  Three  Stars  in  the  belt  of  Orion.  Its  distance  from 
them  is  about  23°.  It  comes  to  the  meridian  at  9  o'clock  on 
the  llth  of  February. 

111.  Mirzam,  in  the  foot  of  the  Dog,  is  a  star  of  the  2d  mag- 
nitude, 5|-0  W.  of  Sirius.     A  little  above,  and  4°  or  5°  to  the 
left,  there  are  three  stars  of  the  3d  and  4th  magnitudes,  forming 
a  triangular  figure  somewhat  resembling  a  dog's  head.     The 
brightest  of  them,  on  the  left,  is  called  Muliphen.     It  entirely 
disappeared  in  1670,  and  was  not  seen  again  for  more  than  20 
years.     Since  that  time  it  has  maintained  a  steady  lustre. 

112.  Wesen  is  a  star  of  between  the  2d  and  3d  magnitudes, 
In  the  back,  11°  S.  S.  E.  of  Sirius,  with  which,  and  Mirzam  in 
the  paw,  it  makes  an  elongated  triangle.     The  two  hinder  feet 
are  marked  by  Naos  and  Lambda,  stars  of  the  3d  and  4th 
magnitudes,  situated  about  3°  apart,  and  12°  directly  S.  of  the 
fore  foot.     This  constellation  contains  31  visible  stars,  including 
one  of  the  1st  magnitude,  four  of  the  2d,  and  two  of  the  3d  ; 
all  of  which  are  easily  traced  out  by  the  aid  of  the  map. 

HISTORY. 

Manilius,  a  Latin  poet  who  flourished  in  the  Augustan  age,  wrote  an  admirable  poem, 
.'  Ive  books,  upon  the  fixed  sta"-",  in  which  he  thus  speaks  of  this  constellation : 
"  All  others  he  excels  ;  no  fairer  light 

Ascends  the  skies,  none  sets  so  clear  and  bright." 
Jt>u.'  EUDOSIA  best  describes  it — 

"  Next  shines  the  Dog  with  sixty-four  distinct ; 
Famed  for  pre-eminence  in  envied  song, 
Theme  of  Homeric  and  Virgilian  lays ; 
His  fierce  mouth  flames  with  dreaded  Siriits  ; 
Three  of  his  stars  retire  with  feeble  beams." 

A-JCOI  ILife-  to  some  mythologists,  this  constellation  represents  one  of  Orion's  hounds, 
ttich  wah  v>lt\ced  in  the  sky,  near  this  celebrated  huntsman.  Others  say  it  received  its 
(.-.me  Jn  bomT  of  the  dog  given  by  Aurora  to  Cephalus,  which  surpassed  in  speed  all  the 

110.  Situ-tu'c    of   Sirius?    What  triangles?        111.  Position  ana  size  of  Miriam  V 
ther  start 7     W'ii"»hen?        112.  Wesen?     What  other  stars ?     Whole  number? 
HISTOUV  --ft.1,*    xassical  description  of  Canis  Major?     What  different  accounts  of  ite 


62  ASTRONOMY. 

animals  of  Lis  species.  Cephalus,  it  is  said,  attempted  to  prove  this  by  running  him 
against  a  fox,  which,  at  that  time,  was  thought  to  be  the  fleetest  of  all  a  limals.  After 
they  had  run  together  a  long  time,  without  either  of  them  obtaining  the  victory,  it  ia 
said  that  Jupiter  was  so  much  gratified  at  the  fleetness  of  the  dog,  that  he  assigned  him 
a  place  in  the  heavens. 

But  the  name  and  form  of  this  constellation  are,  no  doubt,  derived  from  the  Egyp- 
tians, who  carefully  watched  its  rising,  and  by  it  judged  of  the  swelling  of  the  Nile, 
which  they  ca.ied  Siris,  and,  in  their  hieroglyphical  manner  of  writing,  since  it  was,  as 
it  were,  the  sentinel  and  watch  of  the  year,  represented  it  under  the  figure  of  a  dog. 
They  observed  that  when  Sirius  became  visible  in  the  east,  just  before  the  morning  dawn, 
the  overflowing  of  the  Nile  immediately  followed.  Thus  it  warned  them,  like  a  faithful 
dog,  to  escape  from  the  region  of  the  inundation. 

TELESCOPIC  OBJECTS. 

1,  a  CANIS  MAJORIS— A  brilliant  star,  with  a  distant  companion  ;  R.  A.  Ch.  3Sm.  06s.; 
i)ec.  S.  16°  SO'  1.  A  1,  brilliant  white ;  B  10,  deep  yellow,  other  distant  small  stars  in 
the  field. 

2.  6  CANIS  MAJORIS — A  star  with  a  distant  companion  in  the  loins  ;  R.  A.  7h.  Olm.  53s. ; 
Dec,  8-  26*  08'  6".  A  3%,  light  yellow ;  B  7^,  very  pale.  Other  small  stars  in  the  field, 
A  line  from  Betclguese  through  $irius  intercepts  it  12*  below  the  latter  star. 

8.  £  CANIS  MAJORIS  (Adhara) — A  star  with  a  distant  companion  in  the  belly ;  R.  A 
6h.  52m.  20s.    Dec.  S.  28*  45'  5".    A  2%,  pale  orange  :  B  7,  violet.    Found  by  running  a 
-  line  from  the  middle  of  Orion's  belt  through  /3  just  west  of  Sirius,  to  about  14°  beyond 
the  latter  star. 

4.  A  CLUSTER  in  the  back  of  the  head ;  R.  A.  6h.  52m.  10s. ;   Dec.  S.  13°  29'  2".    Tole- 
rably compressed ;  stars  of  the  8th  to  llth  magnitudes,  of  which  the  four  principal 
form  the  letter  Y. 

5.  A  CLUSTER  between  Sirius  and  Monoceros ;  R.  A.  7h.  10m.  85s. ;  Dec.  S.  15°  21'  4' 
Stars  principally  of  the  10th  magnitude.    Discovered  by  Miss  Herschel  in  1785. 


CHAPTER  V. 

CONSTELLATIONS     ON    THE     MERIDIAN     IN    MARCH. 

AEGO  NAVIS  (THE  SHIP  AEGO).— MAP  III. 

113.  THIS  constellation  occupies  a  large  space  in  the  southern 
hemisphere,  though  but  a  small  part  of  it  can  be  seen  in  the 
United  States.     It  is  situated  S.  E.  of  Canis  Major,  and  may 
be  known  by  the  stars  in  the  prow  and  deck  of  the  ship. 

114.  If  a  straight  line  joining  Betelguese  and  Sirius,  be  pro- 
duced 18°  to  the  southeast,  it  will  point  out  N~aos,  a  star  of  the 
2d  magnitude,  in  the  rowlock  of  the  ship.     This  star  is  in  the 
S.  E.  corner  of  the  Egyptian  X,  and  of  the  large  equilateral 
triangle  made  by  itself  with  Sirius  and  the  Dove.     When  on  the 
meridian,  it  is  seen  from  this  latitude  about  8°  above  the  south- 

TELESCOPIC  OBJECTS.— Alpha  ?    Delta?    Epsilon?    What  clusters ? 
113.  Size  and  situation  of  Argo  Navis?    How  kn^wn?        H4.  How  find  2faotjt  nud 
where  situated ?     IIow  high  when  on  the  meridian? 


AUGO    NAVIS.  G3 

cm  horizon.  It  comes  to  the  meridian  on  the  3d  of  March, 
about  half  an  hour  after  Procyon,  and  continues  visible  but  a 
few  hours. 

115.  Gamma,  in  the  middle  of  the  ship,  is  a  star  of  the  2d 
magnitude,  about  7°  S.  of  Naos,  and  just  skims  above  the  south- 
ern horizon  for  a  few  minutes,  and  then  sinks  beneath  it.     The 
principal  star  in  this  constellation  is  called,  after  one  of  the 
pilots,  Canopus;   it  is  of  the  1st  magnitude,  36°  nearly  S.  of 
Sirius,  and  comes  to  the  meridian  1 7  minutes  after  it ;  but  hav- 
ing about  53°  of  S.  declination,  it  cannot  be  seen  in  the  Northern 
States.    The  same  is  true  of  Miaplacidus,  a  star  of  the  1st  magni- 
tude in  the  oars  of  the  ship,  about  25°  E.  of  Canopus,  and  61° 
S.  of  Alphard,  in  the  heart  of  Hydra. 

An  observer  in  the  northern  hemisphere,  can  see  the  stars  as  many  degrees  south  of 
the  equinoctial  in  the  southern  hemisphere,  as  his  own  latitude  lacks  of  90°,  and  no 
more. 

116.  Markeb,  is  a  star  of  the  4th  magnitude,  in  the  prow  of 
the  ship,  and  may  be  seen  from  this  latitude  1 6°  S.  E.  of  Sirius, 
and  about  10°  E.  of  Wesen,  in  the  back  of  the  Dog.     This  star 
may  be  known  by  its  forming  a  small  triangle  with  two  others 
of  the  same  magnitude,  situated  a  little  above  it,  on  the  E.,  3° 
and  4°  apart. 

117.  This  constellation  contains  64  stars,  of  which  two  are 
ot  the  1st  magnitude,  four  of  the  2d,  and  nine  of  the  3d.     Most 
of  these  are  too  low  down  to  be  seen  in  the  United  States. 

HISTORY. 

This  constellation  is  intended  to  perpetuate  the  memory  of  the  famous  ship  which  car- 
ried Jason  and  his  54  companions  to  Colchis,  when  they  resolved  upon  the  perilous 
expedition  of  recovering  the  golden  fleece.  The  derivation  of  the  word  A.TQO  has  been 
often  disputed.  Some  derive  it  from  Argos,  supposing  that  this  was  the  name  of  the 
person  who  first  proposed  the  expedition,  and  built  the  ship.  Others  maintain  that  it 
was  built  at  Argos,  whence  its  name.  Cicero  calls  it  Argo,  because  it  carried  Grecians^ 
commonly  called  Argives.  Diodorus  derives  the  word  from  dp/Of,  which  signifies  swift. 
Ptolemy  says,  but  not  truly,  that  Hercules  built  the  ship,  and  called  it  Argo,  after  a  son 
of  Jason,  who  bore  the  same  name.  This  ship  had  fifty  oars,  and  being  thus  propelled 
must  have  fallen  far  short  of  the  bulk  of  the  smallest  ship  craft  used  by  moderns.  It  is 
even  said  that  the  crew  were  able  to  carry  it  on  their  backs  from  the  Danube  to  the 
Adriatic. 

According  to  many  authors,  she  had  a  beam  on  her  prow,  cut  in  the  forest  of  Dodona 
by  Minerva,  which  had  the  power  of  giving  oracles  to  the  Argonauts.  This  ship  was  the 
first,  it  is  said,  that  ever  ventured  on  the  sea.  After  the  expedition  was  finished,  and 
Jason  had  returned  in  triumph,  he  ordered  her  to  be  drawn  ashore  at  the  isthmus  of 
Corinth,  and  consecrated  to  Neptune,  the  god  of  the  sea. 

Sir  Isaac  Newton  endeavors  to  settle  the  period  of  this  expedition  at  about  30  yeais 

115.  Size  and  situation  of  Gamma?  Name  the  principal  star  in  this  constellation  V 
Its  magnitude?  Is  it  ever  seen  in  the  U.  S. ?  What  said  of  Miaplacidus?  Remark  in 
fine  print?  116.  What  said  of  Markeb?  How  known?  117.  Number  of  stars  in 
Argo  Navis?  Magnitudes? 

HISTOKT.— Design  of  th:s  constellation  ?  Import  of  the  term  A rgof  Size  and  struc- 
ture of  the  ship?  What  myth  respecting  this  ship?  What  remark  respecting  Hb 
Isaac  Newton?  Dr.  Brya  it's  opinion ? 


04  ASTRONOMY. 

before  the  destruction  of  Troy,  and  43  years  after  the  death  of  Solomon.  Dr.  Bryant 
however,  rejects  the  history  of  tl^e  Argonautic  expedition  as  a  mere  fiction  of  the  Greeks, 
and  supposes  that  this  group  of  stars,  which  the  poets  denominate  Argo  Navis,  refers  to 
Noah's  ark  and  the  deluge,  and  that  the  fable  of  the  Argonautic  expedition  is  founded 
on  cei^ain  Egyptian  traditions  that  related  to  the  preservation  of  Is'oah  and  his  family 
during  the  flood. 

TELESCOPIC  OBJECTS. 

«,  ARGO  NAVIS— A  star  with  a  distant  companion ;  R.  A.  8h.  00m.  44s. ;  Dec.  S.  28* 
BO'  8*.    A  3J£,  pale  yellow ;  B  10,  greyish.     Other  small  stars  in  the  field. 

2.  A  SMALL  GALAXY  CLUSTER  ;  R.  A.  7h.  87m.  44s ;  Dec.  S.  28°  29'  1". 

3.  A  neat  DOUBLE  STAR  over  the  ship's  stern  ;  R.  A.  7h.  38m.  08s. ;  Dec.  S.  14°  18'  8". 
A  7,  silvery  white ;  B  7  Jg,  pale  white. 

4.  A  close  DOUBLE  STAR  over  the  Argo's  stern ;  R.  A.  7h.  40m.  27s. ;  Dec.  S.  11*  48'  8" 
A  7^,  pale  yellow ;  B  9,  light  blue. 

5.  A  bright  PLANETARY  NEBULA  ;  R.  A.  7h.  34m.  46s. ;  Dec.  S.  17*  50'  2".    A  fine  object, 
pale  bluish  white,  and  may  be  identified  by  several  small  stars  in  its  vicinity.    See  Map 
V'JIL,  Fig.  37. 


CANCER  (THE  OEAB).— MAP  HJ, 

118.  Cancer  is  now  the  fifth  constellation  and  fourth  sign  ot 
the  Zodiac.     It  is  situated  in  the  ecliptic,  between  Leo  on  the 
E.  and  Gemini  on  the  W.     It  contains  83  stars,  of  which  one  is 
of  the  3d,  and  seven  of  the  4th  magnitude.    Some  place  the  first- 
mentioned  star  in  the  same  class  with  the  other  seven,  and  con- 
sider none  larger  than  the  4th  magnitude. 

119.  Beta  is  a  star  of  the  3d  or  4th  magnitude,  in  the  south- 
western claw,   10°  N.  E.  of  Procyon,  and  may  be  known  from 
the  fact  that  it  stands  alone,  or  at  least  has  no  star  of  the  same 
magnitude  near  it.    It  is  midway  between  Procyon  and  Acubens. 

120.  Acubens,  is  a  star  of  similar  brightness,  in  the  south- 
eastern claw,  10°  N.  E.  of  Beta,  and  nearly  in  a  straight  line 
with  it  and  Procyon.     An  imaginary  line  drawn  from  Capella 
through  Pollux,  will  point  out  Acubens,  at  the  distance  of  24 p 
from  Pollux.     It  may  be  otherwise  distinguished  by  its  standing 
between  two  very  small  stars  close  by  it  in  the  same  claw. 

121.  The  southern  Asellus,  marked  Delta,  is  situated  in  the 
line  of  the  ecliptic,  and,  in  connection  with  Wasat  and  Tejat, 
marks  the  course  of  the  earth's  orbit  for  a  space  of  36°  from 
the  solstitial  colure. 

A  few  degrees  S.  of  Cancer,  and  about  17°  E.  of  Procyon,  are  four  stars  of  the  4th 
magnitude,  3°  or  4°  apart,  which  mark  the  head  of  Hydra.  The  rest  of  this  constellation 
is  delineated  on  Map  IV. 

TELESCOPIC  OBJECTS. — Iota?  What  cluster?  Double  stars?  Nebula?  Point  out  on 
the  map  ? 

IIS.  Place  of  Cancev  in  the  Zodiac?  In  other  respects?  Number  and  size  of  it' 
stars?  119.  Beta?  How  known?  120.  Acubens?  How  found?  121.  Situation 
nf  Delta, ?  Remarks  respecting  Hydra?  Respecting  the  sign  Cancer? 


CANCER.  65 

The  beginning  of  the  sign  Cancer  (not  the  constellation)  is  called  the  Tropic  of  Can- 
jer,  and  when  the  sun  arrives  at  this  point,  it  has  reached  its  utmost  limit  of  north  decli- 
nation, where  it  seems  to  remain  stationary  a  few  days  before  it  begins  to  decline  again 
to  the  south.  This  stationary  attitude  of  the  sun  is  called  the  summer  solstice;  from  two 
Latin  words  signifying  the  sun's  standing  still.  The  distance  from  the  first  point  of 
Cancer  to  the  equinoctial,  which,  at  present,  is  23°  27%',  is  called  the  obliquity  of  the 
ecliptic.  It  is  a  remarkable  and  well  ascertained  fact,  that  this  is  continually  growing 
less  and  less.  The  tropics  are  slowly  and  steadily  approaching  the  equinoctial,  at  the 
rate  of  about  half  a  second  every  year ;  so  that  the  sun  does  not  now  come  so  far  north 
of  the  f  quator  in  summer,  nor  decline  so  far  south  in  winter,  as  it  must  have  done  at  the 
creation,  by  nearly  a  degree. 

HISTORY. 

In  the  Zodiacs  of  Esne  and  Dendera,  and  in  most  of  the  astrological  remains  of  Egypt, 
n  Scairabaeus,  or  Beetle,  is  used  as  the  symbol  of  this  sign ;  but  in  Sir  William  Jones' 
Oriental  Zodiac,  and  in  some  others  found  in  India,  we  meet  with  the  figure  of  a  crab. 
As  the  Hindoos,  in  all  probability,  deriw.  J  their  knowledge  of  the  stars  from  the  Chal- 
deans, it  is  supposed  that  the  figure  of  the  crab,  in  this  place,  is  more  ancient  than  the 
Beetle. 

In  some  ea  stern  representations  of  this  sign,  two  animals,  like  asses,  are  found  in  this 
division  of  L.e  Zodiac;  and  as  the  Chaldaic  name  for  the  ass  may  be  translated  muddi- 
ness,  it  is  supposed  to  allude  to  the  discoloring  of  the  Nile,  which  river  was  rising  when 
the  sun  ente-ed  Cancer.  The  Greeks,  in  copying  this  sign,  have  placed  two  asses  as  the 
appropriate  symbol  of  it,  which  stal  remain.  They  explain  their  reason,  however,  for 
adopting  this^gure,  by  saying  that  these  are  the  animals  that  assisted  Jupiter  in  hia 
victory  over  the  giants. 

Dopuis  accounts  for  the  origin  of  the  asses  in  the  following  words : — "  Le  Cancer  oil 
sont  les  etoiles  appellees  les  anes,  forme  1'empreinte  du  pavilion  d'  Issachar  que  Jacob 
assimile  a  1'ane." 

Mytholog'sts  give  different  accounts  of  the  origin  of  this  constellation.  The  prevail- 
ing opinion  ,s,  that  while  Hercules  was  engaged  in  his  famous  contest  with  the  dreadful 
Lernsean  monster,  Juno,  envious  of  the  fame  of  his  achievements,  sent  a  sea-crab  to 
bite  and  an  icy  the  hero's  feet,  but  the  crab  being  soon  dispatched,  the  goddess,  to  reward 
its  services,  placed  it  among  the  constellations. 

"  The  Scorpion's  claws  here  clasp  a  wide  extent, 
And  here  the  Crab's  in  lesser  clasps  are  bent." 

TELESCOPIC  OBJECTS. 

1.  d  CANCRI — A  very  delicate  DOUBLE  STAR,  under  the  Crab's  mouth  ;•  R.  A.  8h.  35m. 
£5s. ;  Dec.   1. 18°  44'  04".    A  4J^,  straw  color ;  B  15  blue,  only  seen  by  glimpses. 

2.  £  CANCRI — A  star  with  a  distant  companion,  on  the  Crab's  body ;  R.  A.  8h.  31m. 
16s.;  Dec.  N.  20°  06'  02'.    A  6%,  and  B  7,  both  pale  white ;  and  a  third  star  in  the  field 
of  nearly  Uie  same  magnitude. 

3.  (,  CANCRI — A  fine  TRIPLE  STAR,  just  below  the  after  claws  of  the  Crab;  R.  A.  8h.  03m. 
02s.;  Dec.   N.  18°  07'  05".    A  6,  yellow;  B  7,  orange  tinge;  C  7%,  yellowish.    Supposed 
to  be  a  Ternary  system. 

4.  Abort  7"  northeasterly  from  Tegmine,  is  a  nebulous  cluster  of  very  minute   stars,  in 
the  crest  of  Cancer,  sufficiently  luminous  to  be  seen  by  the  naked  eye.    It  is  situated  in 
a  triangular  position  with  regard  to  the  head  of  the  Twins  and  the  Little  Dog.    It  is  about 
20°  W.  of  ^ach.    It  may  otherwise  be  discovered  by  means  of  two  conspicuous  stars  of 
the  4th  magnitude,  lying  one  on  either  side  of  it,  at  the  distance  of  about  2°,  called  the 
northern  and  southern  Aselli.    Bj  some  of  the  Orientalists,  this  cluster  was  denominated 
Prcesepe,  .he  Manger,  a  contrivance  which  their  fancy  filled  up  for  the  accommodation 
cf  the  Aselli  or  Asses;  and  it  is  so  called  by  modern  astronomers.    The  appearance  of 
this  group  to  the  unassisted  eye,  is  not  unlike  the  nucleus  of  a  comet,  and  it  was  repeat- 
edly mistaken  for  the  comet  of  1832,  which,  in  the  month  of  November,  passed  in  its 
neighborhood.    Map  VIII.,  Fig.  38. 

5.  A  P-CH  BUT  LOOSE  CLUSTER  in  the  Crab's  southern  claw,  where  a  line  from  Rigel 
through  Procyon,  into  the  east-northeast,  will  find  it  about  5°  north  of  e  in  the  Hyades  ; 
R.  A.  8h.  42m.  26s. ;  Dec.  N.  12°  23'  06".    Stars  mostly  of  the  9th  and  10th  magnitudes. 
See  Map  VIII.,  Fig.  39. 

HISTO-.*.— What  other  figures  for  Cancer?    Egyptian?    Hindoo?    Greek?    Oriein  oJ 
this  cor  'ellation? 
TELESCOPIC  OBJECTS.— Delta  ?    Ef  silon  ?    Ze\a  ?    What  Clusters  ?    Point  out  on  the  Mar 


66  ASTRONOMY. 

CHAPTER  VI. 

CONSTELLATIONS    ON   THE    MERIDIAN    IN    APRIL. 

LEO  (THE  LION).— MAP  IV. 

122.  LEO  is  one  of  the  most   brilliant  constellations  in  the 
winter  hemisphere,   and  contains   an  unusual  number  of  very 
bright  stars.     It  is  situated*  next  E.  of  Cancer,  and  directly  S. 
of  Leo  Minor  and  the  Great  Bear. 

The  Hindoo  astronomer,  Varaha,  says,  "  Certainly  the  southern  solstice  was  once  in 
the  middle  of  Asleha  (Leo) ;  the  northern  in  the  first  degree  of  Dhanishta"  (Aquarius). 
Since  that  time,  the  solstitial,  as  well  as  the  equinoctial  points,  have  gone  backward  on 
the  ecliptic  75°.  This  divided  by  50%",  gives  5373  years  ;  which  carry  us  back  to  the 
year  of  the  world  464.  Sir  W.  Jones  says,  that  Varaha  lived  when  the  solstices  were  in 
the  first  degrees  of  Cancer  and  Capricorn ;  or  about  400  years  before  the  Clyistian  era. 

123.  Leo  is  the  fifth  sign,  and  the  sixth  constellation  of  the 
Zodiac.     The  mean  right  ascension  of  this  extensive  group  is 
150°,  or  10  hours.     Its  center  is  therefore  on  the  meridian  the 
sixth   of  April.     Its  western  outline,   however,   comes  to  the 
meridian  on  the  18th  of  March,  while  its  eastern  limit  does  not 
reach  it  before  the  3d  of  May. 

This  constellation  contains  95  visible  stars,  of  which  one  is 
of  the  1st  magnitude,  one  of  the  2d,  six  of  the  3d,  and  fifteen  of 
the  4th. 

"  One  splendid  star  of  highest  dignity, 
One  of  the  second  class  the  Lion  boasts, 
And  justly  figures  the  fierce  summer's  rage." 

124.  The  principal  star  in  this  constellation  is  of  the  1st  mag- 
nitude, situated  in  the  breast  of  the  animal,  and  named  Regulus, 
from  the  illustrious  Roman  consul  of  that  name. 

It  is  situated  almost  exactly  in  the  ecliptic,  and  may  be 
readily  distinguished  on  account  of  its  superior  brilliancy.  It  is 
the  largest  and  lowest  of  a  group  of  five  or  six  bright  stars 
which  form  a  figure  somewhat  resembling  a  sickle,  in  the  neck 
and  shoulder  of  the  Lion.  There  is  a  little  star  of  the  5th  mag- 
nitude, about  2°  S.  of  it,  and  one  of  the  3d  magnitude  5°  N.  of 
it,  which  will  serve  to  point  it  out. 

Great  use  is  made  of  Regulus  by  nautical  men,  for  determining  their  longitude  at  sea. 
Its  latitude,  or  distance  from  the  ecliptic,  is  less  than  j£°;  but  its  declination,  or  dis- 
tance from  the  equinoctial,  is  nearly  13°  N. ;  so  that  its  meridian  altitude  will  be  just 

122.  Describe  Leo.  Its  situation  ?  What  remarkable  statement  of  Varaha?  Calcula- 
tions upon  it?  123.  Position  of  Leo  in  the  Zodiac  ?  When  on  the  meridian?  Number 
and  size  of  its  stars  ?  124.  Its  principal  star?  Situation?  How  distinguished?  What 
ijse  made  of  Regulus  ?  When  on  the  meridian,  where  are  Castor  and  Pollux  ? 


LEO.  67 

equal  to  that  of  the  sun  on  the  19th  of  August.    Its  right  ascension  is  very  nearly  150*. 
It  therefore  culminates  about  9  o'clock  on  the  6th  of  April. 

When  Regulus  is  on  the  meridian,  Castor  and  Pollux  are  seen  about  40°  N.  W.  of  it, 
and  the  two  stars  in  the  Little  Dog  are  about  the  same  distance  in  a  S.  W.  direction ; 
with  which,  and  the  two  former,  it  makes  a  large  isosceles  triangle  whose  vertex  is  at 
Hegulua. 

125.  The  next  considerable  star  is  5°  N.  of  Regulus,  marked 
Eta,  situated  in  the  collar  ;  it  is  of  between  the  3d  and  4th 
magnitudes,  and  with  Regulus   constitutes  the  handle  of  the 
sickle.     Those  three  or  four  stars  of  the  3d  magnitude,  N.  and 
W.  of  Eta,  arching  round  with  the  neck  of  the  animal,  describe 
the  blade. 

126.  Al  Gieba  is  a  bright  star  of  the  2d  magnitude,  situated 
in  the  shoulder,  4°  in  a  N.  E.  direction  from  Eta,  and  may  be 
easily  distinguished  by  its  being  the  brightest  and  middle  one  of 
the  three  stars  lying  in  a  semicircular  form  curving  toward  the 
west ;  and  it  is  the  first  in  the  blade  of  the  sickle. 

12T.  Adhafera  is  a  star  of  the  3d  magnitude,  situated  in  the 
neck,  4°  N.  of  Al  Gieba,  and  may  be  known  by  a  very  minute 
star  just  below  it.  This  is  the  second  star  in  the  blade  of  the 
sickle. 

128.  Ras  al  Asad,  situated  before  the  ear,  is  a  star  of  the  3d 
or  4th  magnitude,  6°  W.  of  Adhafera,  and  is  the  third  in  the 
blade  of  the  sickle.     The  next  star,  Epsilon,  of  the  same  magni- 
tude, situated  in  the  head,  is  2£°  S.  W.  of  Ras  al  Asad,  and  a 
little  within  the  curve  of  the  sickle.     About  midway  between 
these,  and  a  little  to  the  E.,  is  a  very  small  star  hardly  visible 
to  the  naked  eye. 

129.  Lambda,   situated  in  the  mouth,  is  a  star  of  the  4th 
magnitude,  3£°  S.  W.  of  Epsilon,  and  the  last  in  the  sickle's 
point.     Kappa,  situated  in  the  nose,  is  another  star  of  the  same 
magnitude,  and  about  as  far  from  Lambda  as  Epsilon.     Epsilon 
and  Kappa  are  about  4^-°  apart,  and  form  the  longest  side  of  a 
triangle,  whose  vertex  is  in  Kappa. 

130.  Zozma,  situated  in  the  back  of  the  Lion,  is  a  star  of  the 
3d  magnitude  18°  N.  E.  of  Regulus,  and  midway  between  it  and 
Coma  Berenices,  a  fine  cluster  of  small  stars,  18°  N.  E.  of 
Zozma. 

131.  Theta,  situated  in  the  thigh,  is  another  star  of  the  3d 
magnitude,  5°  directly  S.  of  Zozma,  and  so  nearly  on  the  same 
meridian  that  it  culminates  but  one  minute  after  it.     This  star 


125.  Next   principal   star — size   and   position?  126.  Al   Gieba?      How  known? 

12T.  Adhafera?        128.  Ras  al  Asad?    Epsilon?  129.  Situation  and  size  of  Lambda* 

Of  Kappa?        180.  Of  Zo/ma?        181.  Of  Theta?  What  triangle?     What  other  stars 
mentioned? 


b8  ASTRONOMY. 

makes  a  right-angled  triangle,  with  Zozma  on  the  N.  and  Dene- 
bola  on  the  E.,  the  right  angle  being  at  Theta. 

Nearly  in  a  straight  line  with  Zozma  and  Theta,  and  sonth 
of  them,  are  three  or  four  smaller  stars,  4°  or  5°  apart,  which 
mark  one  of  the  legs. 

132.  Dentbola  is  a  bright  star  of  the  first  magnitude,  in  the 
brush  of  the  tail,  10°  S.  E.  of  Zozma,  and  may.  be  distinguished 
by  its  great  brilliancy.  It  is  5°  W.  of  the  equinoctial  colure, 
and  comes  to  the  meridian  1  hour  and  41  minutes  after  Regulus, 
on  the  3d  of  May  ;  when  its  meridian  altitude  is  the  same  as 
the  sun's  at  12  o'clock  the  next  day. 

When  Denebola  is  on  the  meridian,  Regulus  is  seen  25"  W.  of  it,  and  Phad,  in  the 
square  of  Ursa  Major,  bears  39°  N.  of  it.  It  forms,  with  these  two,  a  large  right-angled 
triangle ;  the  right  angle  being  at  Denebola.  It  is  so  nearly  on  the  same  meridian  with 
Phad  that  it  culminates  only  four  minutes  before  it. 

Denebola  is  35V  W.  of  Arcturus,  and  about  the  same  distance  N.  W.  of  Spica  Vir- 
ginis,  and  forms,  with  them,  a  large  equilateral  triangle  on  the  S.  E.  It  also  forms  with 
Arcturus  and  Cor  Caroli  a  similar  figure,  nearly  as  large  on  the  N.  E.  These  two 
triangles,  being  joined  at  their  base,  constitute  a  perfect  geometrical  figure  of  the  form 
of  a  Rhombus,  called  by  some,  the  DIAMOND  OF  VIRGO. 

A  line  drawn  from  Denebola  through  Regulus,  and  continued  7*  or  8°  further  in  the 
same  direction,  will  point  out  Xi  and  Omicron,  of  the  3d  and  4th  magnitudes,  situated 
in  the  foreclaws,  and  about  3°  apart. 

There  are  a  number  of  other  stars  of  the  3d  and  4th  magnitudes  in  this  constellation, 
which  require  no  description,  as  the  scholar  will  easily  trace  them  out  from  the  map. 
The  position  of  Regulus  and  Denebola  are  often  referred  to  in  the  geography  of  the 
heavens,  as  they  serve  to  point  out  other  clusters  in  the  same  neighborhood. 

HISTORY. 

According  to  Greek  fable,  this  Lion  represents  the  formidable  animal  which  infested 
the  forests  of  Nemaea.  It  was  slain  by  Hercules,  and  placed  by  Jupiter  among  the  stars 
in  commemoration  of  the  dreadful  conflict.  Some  writers  have  applied  the  story  of  the 
twelve  labors  of  Hercules  to  the  progress  of  the  sun  through  the  twelve  signs  of  the 
ecliptic ;  and  as  the  combat  of  that  celebrated  hero  with  the  Lion  was  his  first  labor, 
they  have  placed  Leo  as  the  first  sign.  The  figure  of  the  Lion  was,  however,  on  the 
Egyptian  charts  long  before  the  invention  of  the  fables  of  Hercules.  It  would  seem, 
moreover,  according  to  the  fable  itself,  that  Hercules,  who  represented  the  sun,  actually 
slew  the  Nemaean  Lion,  because  Leo  was  already  a  zodiacal  sign. 

In  hieroglyphical  writing  the  Lion  was  an  emblem  of  violence  and  fury;  and  the 
representation  of  this  animal  in  the  Zodiac,  signified  the  intense  heat  occasioned  by  the 
sun  when  it  entered  that  part  of  the  ecliptic.  The  Egyptians  were  much  annoyed  by 
lions  during  the  heat  of  summer,  as  they  at  that  season  left  the  desert,  and  haunted  the 
banks  of  the  Nile,  which  had  then  reached  its  greatest  elevation.  It  was  therefore 
natural  for  their  astronomers  to  place  the  Lion  where  we  find  him  in  the  Zodiac. 

The  figure  of  Leo,  very  much  as  we  now  have  it,  is  in  all  the  Indian  and  Egyptian 
Zodiacs.  The  overflowing  of  the  Nile,  which  was  regularly  and  anxiously  expected  every 
year  by  the  Egyptians,  took  place  when  the  sun  was  in  this  sign.  They  therefore  paid 
more  attention  to  it,  it  is  to  be  presumed,  than  to  any  other.  This  was  the  principal 
reason,  Mr.  Green  supposes,  why  Leo  stands  first  in  the  zodiacs  of  Dendera. 

In  the  Hebrew  Zodiac,  Leo  is  assigned  to  Judah,  on  whose  standard,  according  to  rJ. 
traditions,  a  Lion  is  painted.  This  is  clearly  intimated  in  numerous  passages  of  the 
Hebrew  writings :  Ex. — "  Judah  is  a  Lion's  whelp ;  he  stooped  down,  he  couched  as  a 

132.  Size  and  position  of  Denebola?  How  known  ?  When  does  it  come  to  the  meri- 
dian as  compared  with  Regulus?  What  said  of  its  meridian  altitude?  When  on  the 
meridian  where  is  Regulus  seen?  Phad?  What  triangle?  How  is  Denebolo  situated 
with  respect  to  Arcturus  and  Spica  Virginis  ?  To  Cor  Caroli  ?  What  other  large  figures 

HISTORY.— Greek  fable?  Egyptian?  Hebrew  Zodiacs?  Scripture  allusions  to  thf 
t-'cn? 


LEO    MINOR.  69 

L!on,  and  as  an  Old  Lion ;  who  shall  rouse  him  up  ?"  Gen.  xlix.  9.    "  The  Lion  of  the 
tribo  of  Judah  hath  prevailed."  Rev.  v.  5. 

TELESCOPIC  OBJECTS 

I.  a  LEONIS  (Rtguliu) — A  bright  star  with  a  distant  companion ;  R.  A.  9h.  59m.  51a. ; 
Dec.  N.  12*  44'  08".    A  1,  flushed  white ;  B  8%,  pale  purple. 

2  8  LEONIS  (Denebola}—^  fine  star  with  a  distant  companion ;  R.  A.  lib.  40m.  54s.  j 
D«c.  N.  15°  28'  0".  A  2^,  bluish ;  B  8,  dull  red. 

8.  y  LEONfs(^  Gieba)—A.  splendid  DOUBLE  STAB;  R.  A.  lOh.  llm.  08s.;  Dec.  N.  20° 
89'  0".  A  2,  bright  orange;  B  4,  greenish  yellow.  A  most  beautiful  object — binary- 
period  supposed  about  1000  years.  Map  V1IL,  Fig.  6. 

4.  6  LEONIS  (Zozma)—A.  coarse  TRIPLE  STAB;  R.  A.  llh.  05m.  35s. ;  Dec.  N.  21°  24'  1*. 
A  3,  pale  yellow  ;  B  13,  blue  ;  C  9,  violet. 

5.  e  LEONIS — A  star  with  a  distant  companion  in  the  mouth  of  Leo ;  R.  A.  9h.  30m.  46s  ; 
Dec.  N.  24°  30'  5".    A  3,  yellow ;  B  10,  pale  grey. 

6.  i  LEONIS — A  BINARY  STAR  in  the  flank,  7°  S.  W.  of  Denebola  (F  on  map;;  R.  A.  llh. 
15m.  85s. ;  Dec.  N.  11*  24'  8".    It  forms  a  neat  scalene  triangle  with  (3  and  &.    A  4,  pale 
yellow  ;  B  7 % ,  light  blue  ;  a  beautiful  object. 

7.  /j,  LEONIS  (Bas  Al  Asad)—A  DOUBLE  STAB  ;  R.  A.  9h.  43m.  89s. ;  Dec.  N.  26*  46'  5'. 
A  3,  orivnge  ;  B  10,  pale  lilac. 

8.  A  neat  DOUBLE  STAR  near  Zozma  ;  R.  A.  llh.  05m.  17s. ;  Dec.  21°  00'  8'.  Components 
both  7J6,  and  both  faint  yellow;  a  beautiful  object. 

9.  A  BRIGHT  NEBULA  near  the  hind  paws ;  R.  A.  lOh.  57m.  37s. ;  Dec.  N.  0°  49'  6".  Large, 
elongated,  well-defined — an  enormous  mass  of  luminous  matter — one  of  a  vast  number 
of  spherical  nebulae  in  the  vicinity. 

10.  A  bicentral  WHITE  NEBULA  in  the  lower  jaw,  2"  south  of  /I  Leonis  ;  R.  A.  9h.  23m. 
07s. ;  Dec.  N.  22°  1 2'  1".     May  be  classed  as  double— small  stars  in  field  ;  difficult  object. 
See  Map  VIII.,  Fig.  40. 

II.  A  lucid  WHITE  NEBULA  on  the  Lion's  ribs,  about  9"  due  east  of  Regulus ;  R.  A.  lOh. 
35m.  81s. ;  Dec.  N.  12°  31'  9".    Round  and  bright,  with  two  small  stars  in  field.    Another 
large  pale  white  nebula,  about  1°  east  of  it. 

12.  A  PAIR  OP  BRIGHT  CLASS  NEBULA  in  the  Lion's  belly ;  R.  A.  lOh.  39m.  49s. ;  Dec.  N. 
13°  28'.    Found  south   of  line  joining  Regulus  and  $  Leonis,  about  10"  east  of,  and 
nearly  on  a  parallel  with  the  latter. 

13.  A  LARGE,  ELONGATED  NEBULA,  with  a  bright  nucleus  on  the  Lion's  haunch;  R.  A. 
llh.  llm.  48s. ;  Dec.  N.  13"  52'  4" ;  just  3"  southeast  of  #,  with  another  smaller  nebula, 
and  several  stars  in  the  field.    Map  VIII.,  Fig.  41. 

LEO  MINOR  (THE  LITTLE  LION).— MAP  IY. 

133.  Leo  Minor  contains  53  stars,  including  only  one  of  thu 
3d  magnitude,  and  five  of  the  4th.  The  principal  star  is  situated 
in  the  body  of  the  animal,  13°  N.  of  Gamma  Leonis,  in  a  straight 
line  with  Phad,  and  may  be  known  by  a  group  of  smaller  stars, 
a  little  above  it  on  the  N.  W. 

It  forms  an  equilateral  triangle  with  Gamma  and  Delta  Leonis,  the  vertex  being  in 
Leo  Minor.  This  star  is  marked  with  the  letter  I,  in  modern  catalogues,  and  being  the 
principal  representative  of  the  constellation,  is  itself  sometimes  called  the  Little  Lion: 
8'  E.  of  this  star  (the  Little  Lion)  are  two  stars  of  the  4th  magnitude,  in  the  last  paw 
of  Ursa  Major,  and  about  10°  N.  W.  of  it  are  two  other  stars  of  the  3d  magnitude,  in  the 
first  hind  paw. 

"  The  Smaller  Lion  now  succeeds ;  a  cohort 
Of  fifty  stars  attend  his  steps  ; 
And  three,  to  sight  unarm'd,  invisibl  •«.'•' 

TELESCOPIC    OBJECTS.— Alpha ?     Beta?     Gamma?     -Point  out  on  the  map.     Dclti? 
Epoilou?     Iota?     Mu?     What  nebulae?     Which  shown  on  the  map ?     Point  out. 
183.  Describe  Leo  Minor  ?    Its  principal  star  ?     Helps  form  what  triangle  ? 


70  ASTRONOMY. 

134.  This  constellation  was  formed  by  Hevelius,  out  ol  the 
Stella  informes,  or  unformed  stars  of  the  ancients,  which  lay 
scattered  between  the  Zodiacal  constellation  Leo  on  the  S.,  and 
Ursa  Major  on  the  N.  Its  mean  right  ascension  •  is  the  same 
with  that  of  Regulus,  and  it  comes  to  the  meridian  at  the  same 
time  on  the  6th  of  April. 

The  modern  constellations,  or  those  which  have  been  added  to  our  celestial  maps 
B'nce  the  adoption  of  the  Greek  notation,  in  1603,  are  referred  to  by  the  letters  of  the 
English  alphabet  instead  of  the  Greek.  This  is  the  case  in  regard  to  Leo  Minor,  and  all 
other  constellations  whose  origin  is  subsequent  to  that  period. 

TELESCOPIC  OBJECTS. 

A  BRIGHT  OVAL  NEBULA  between  Lynx  and  Cancer,  but  given  to  Leo  Minor ;  R.  A.  8h. 
42m.  44s. ;  Dec.  N.  34°  00'  6".  Direct  telescope  16°  north  by  east  of  Presepe  in  Cancer 


SEXTANS  (THE  SEXTANT).— MAP  IV. 

135.  Sextans  contains  41  very  small  stars,  including  only  one 
as  large  as  the  4th  magnitude.  This  is  situated  very  near  the 
equinoctial,  1 3°  S.  of  Regulus,  and  comes  to  the  meridian  about 
the  same  time  on  the  6th  of  April.  The  other  stars  in  this  con- 
stellation are  too  small  to  engage  attention.  A  few  of  the 
largest  of  them  may  be  traced  out  from  the  map. 

The  SEXTANT,  called  also  URANIA'S  SEXTANT,  is  a  modern  constellation  that  Hevelius 
made  out  of  the  unformed  stars  of  the  ancients,  which  lay  scattered  between  the  Lion 
on  the  N.,  and  Hydra  on  the  S. 

Urania  was  one  of  the  muses,  and  daughter  of  Jupiter  and  Mnemosyne.  She  pre- 
sided over  astronomy.  She  was  represented  as  a  young  virgin,  dressed  in  an  azure- 
colored  robe,  crowned  with  stars,  holding  a  robe  in  her  hands,  and  having  many  mathe- 
matical instruments  about  her. 

A  sextant,  in  mathematics,  is  the  sixth  part  of  a  circle,  or  an  arc  comprehending  60 
degrees.  But  the  term  is  more  particularly  used  to  denote  an  astronomical  instrument 
well  known  to  mariners.  Its  use  is  the  same  as  that  of  the  quadrant:  namely,  to  mea- 
sure the  angular  distance,  and  take  the  altitude  of  the  suri,  moon,  planets,  and  fixed 
stars.  It  is  indispensable  to  the  mariner  in  finding  the  latitude  and  longitude  at  sea, 
and  should  be  in  the  hands  of  every  surveyor  and  practical  engineer.  It  may  serve  the 
purpose  of  a  theodolite,  in  measuring  inaccessible  heights  and  distances.  It  may  gra- 
tify the  young  pupil  to  know,  that  by  means  of  such  an  instrument,  well  adjusted,  and 
with  a  clear  eye  and  a  steady  hand,  he  could  readily  tell,  within  a  few  hundred  yards 
how  far  north  or  south  of  the  equator  he  was,  and  that  from  any  quarter  of  the  world, 
known  or  unknown.  This  constellation  is  BO  called,  on  account  of  a  supposed  resem- 
blance to  this  instrument. 

TELESCOPIC  OBJECTS. 

1.  A  DOUBLE  STAR  on  the  right  fore  leg  of  Leo,  though  crimped  into  the  sextant ;  R.  A 
9h.  45m.  45s. ;  Dec.  N.  5°  41'  S".  It  lies  about  one-third  of  the  way  from  Regulus  to 
Alphard.  A  7,  and  B.  9,  both  blue,  and  well-defined. 

134.  Origin  of  Leo  Minor?    Mean  R.  A.?    What  remark  respecting  the  notation  of 
ihe  stars  ? 

TELESCOPIC  OBJECTS.— What  nebula?    Situation?    How  find? 

135.  Describe  Sextans  ?    Situation  of  its  principal  star  ?    What  said  of  the  remainder  ? 
What  said  of  the  age  of  this  constellation  ?    Of  Urania  ?    Of  the  Sextant  as  a  nautical 
instrument?  . 

TELESCOPIC  OBJECTS.— What  double  stars?  What  nebula?  What  *x.nnrkable  sigh4 
seen  near  this  nebula! 


HYDRA.  71 

2.  A  neat  DOUBLE  STAR  on  the  north  extreme  of  the  graduated  limb  of  the  instrument; 
nnd  three-fifths  of  the  distance  oetween  Alphard  and  Denebola  ;  R.  A.  lOh.  35m.  02s.; 
Dec.  N.  5°  85'  2".  A  7,  topaz  yellow;  B  8,  smalt  blue  ;  a  fine  object. 

8.  A  bright  class  ROUND  NEBULA  on  the  frame  of  the  instrument ;  R.  A.  lOh.  05m.  68s.; 
Dec.  N.  4°  15'  1".  A  good  telescope  shows  another  large  but  faint  nebula  near  by. 

This  object  is  on  or  near  the  spot  where  the  Capuchin,  De  Rheita,  fancied  he  saw  th« 
napkin  of  St.  Veronica,  in  1783.  Captain  Smyth  has  a  picture  of  this  wonderful  napkin  ; 
and  Sir  J.  Herschel  remarks  that  "  many  strange  things  were  seen  among  the  stars 
Deforo  the  use  of  powerful  telescopes  became  common." 

HYDRA  AND  THE  CUP.— MAP  IY. 

136.  HYDRA,   (the  Water- Serpent,}  is  an  extensive  constella- 
tion, winding  from  E.  to  W.  in  a  serpentine  direction,  over  a 
space  of  more  than  100.  degrees  in  length.     It  lies  south  of 
Cancer,  Leo  and  Yirgo,  and  reaches  almost  from  Canis  Minor 
to  Libra.     It  contains  sixty  stars,  including  one  of  the  2d  mag- 
nitude, three  of  the  3d,  and  twelve  of  the  4th. 

137.  Alphard  or  Cor  Hydra,  in  the  heart,  is  a  lone  star  of 
the  2d  magnitude,  23°  S.  S.  W.  of  Regulus,  and  comes  to  the 
meridian  at  the  same  time  with  Lambda,  in  the  point  of  the 
sickle,  about  20  minutes  before  9  o'clock  on  the  1st  of  April. 
There  is  no  other  considerable  star  near  it,  for  which  it  can  be 
mistaken.      An   imaginary   line    drawn    from    Gamma   Leonis 
through  Kegulus,  will  point  out  Cor  Hydrse,  at  the  distance 
of  23°. 

138.  The  head  of  Hydra  may  be  distinguished  by  means  of 
four  stars  of  the  4th  magnitude,  2^-°  and  4°  apart,  situated  6° 
S.  of  Acubens,  and  forming  a  rhomboidal  figure.     The  three 
upper  stars  in  this  cluster  form  a  small  arch,  and  may  be  known 
by  two  very  small  stars  just  below  the  middle  one,  making  with 
it  a  very  small  triangle.     The  three  western  stars  in  the  head 
also  make  a  beautiful  little  triangle.     The  eastern  star  in  this 
group,  marked  *Zeta,  is  about  6°  directly  S.  of  Acubens,   and 
culminates  at  the  same  time. 

139.  When  Alphard  is  on  the  meridian,  Alkes,  of  the  4th  mag- 
nitude, situated  in  the  bottom  of  the  Cup,  may  be  seen  24°  S.  E. 
of  it,  and  is  distinguished  by  its  forming  an  equilateral  triangle 
with  Beta  and  Gamma,  stars  of  the  same  magnitude,  6°  S.  and 
E.  of  it.     Alkes  is  common  both  to  Hydra  and  the  Cup.     Beta, 
on  the  S.,  is  in  Hydra,  and  Gamma,  on  the  N.  E.,  is  near  the 
middle  of  the  Cup.     A  line  drawn  from  Zozma,  through  Theta 

136.  Describe  Hydra?  Its  situation  ?  Number  and  magnitude  of  its  stars?  187.  Po- 
situ  n  and  magnitude  of  Alphard  ?  How  pointed  out?  138.  How  i»  the  head  of  Hydra 
distinguished?  139.  What  said  of  Alkes?  Of  Beta  and  Gamma?  Hor  is  Beta 
found  ? 


Y2  ASTRONOMY. 

Leoiiis,  and  continued  38J°  directly  S.  will  reach  Beta  ;  it  is 
therefore  on  the  same  meridian,  and  will  culminate  at  the  saino 
time  on  the  23d  of  April. 

140.  The  Cup  itself  (called  also  the  Crater],  may  be  easily 
distinguished  by  means  of  six  stars  of  the  4th  magnitude,  form- 
ing a  beautiful  crescent,  or  semicircle  ,  opening  to  the  W.     The 
center  of  tbis  group  is  about  15°  below  the  equinoctial,   and 
directly  S.  of  the  hinder  feet  of  Leo.     The  crescent  form  of  the 
stars  in  the  Cup  is  so  striking  and  well  defined,  when  the  moon 
is  absent,  that  no  other  description  is  necessary  to  point  them 
out.     Its  center  comes  to  the  meridian  about  two  hours  after 
Alphard,  on  the  same  evening  ;  and  consequently,  it  culminates 
at  9  o'clock,  one  month  after  Alphard  does.     The  remainder  of 
the  stars  in  this  constellation  may  be  easily  traced  by  aid  of 
the  map. 

141.  When  the  head  of  Hydra  is  on  the  meridian,  its  other 
extremity  is  many  degrees  below  the  horizon,  so  that  its  whole 
length  cannot  be  traced  out  in  the  heavens  until  its  center,  or 
the  Cup,  is  on  the  meridian. 

"  Near  the  equator  rolls 

The  sparkling  Hydra,  proudly  eminent 
To  drink  the  Galaxy's  refulgent  sea; 
Nearly  a  fourth  of  the  encircling  curve 
Which  girds  the  ecliptic,  his  \ast  folds  involve; 
Yet  ten  the  number  ol  his  stars  diffused 
O'er  the  long  track  of  his  enormous  spires  ; 
Chief  beams  his  heart,  sure  of  the  second  rank, 
But  emulous  to  gain  the  first." — Eudonia. 

HISTORY. 

ihe  astrologers  of  the  east,  in  dividing  the  celestial  hosts  into  various  compartments, 
assigned  a  popular  and  allegorical  meaning  to  each.  Thus  the  sign  Leo,  which  passee 
the  meridian  about  midnight,  when  the  sun  is  in  Pisces,  was  called  the  House  of  tht, 
Lions,  Leo  being  the  domicil  of  Sol. 

The  introduction  of  two  serpents  into  the  constellations  of  the  ancients,  had  its  origin 
it  is  supposed,  in  the  circumstances  that  the  polar  one  represented  the  oblique  course  of 
the  stars,  while  the  Hydra,  or  Great  Snake,  in  the  southern  hemisphere,  symbolized  the 
moon's  course  ;  hence  the  Nodes  are  called  the  Dragon's  head  and  tail  to  this  day, 

The  hydra  was  a  terrible  monster,  which,  according  to  mythologists,  infested  tin 
neighborhood  of  the  lake  Lerna,  in  the  Peloponnesus.  It  had  a  hundred  heads,  accord- 
Ing  to  Diodorous ;  fifty,  according  to  Simonides ;  and  nine,  according  to  the  more  com 
monly  received  opinion  of  Apollodorus,  Hyginus,  and  others.  As  soon  as  one  of  these 
heads  was  cut  off,  two  immediately  grew  up  if  the  wound  was  not  stopped  by  fire. 

"  Art  thou  proportion'd  to  the  hydra's  length, 
Who  by  his  wounds  received  augmented  strength? 
He  raised  a  hundred  hissing  heads  in  air, 
When  one  I  lopp'd,  up  sprang  a  dreadful  pair." 

To  destroy  this  dreadful'monster,  was  one  of  the  labors  of  Hercules,  and  this  he  easily 
effected  with  the  assistance  of  lolaus,  who  applied  a  burning  iron  to  the  wounds  as 
soon  as  one  head  was  cut  off.  While  Hercules  was  destroying  the  hydra,  Juno,  jealous  of 
lis  glory,  sent  a  sea-crab  to  bite  his  foot.  This  new  enemy  was  soon  despatched ;  an  1 

140.  How  is  the  Gup  distinguished  ?  Is  it  easily  found  ?  141.  What  id  said  of  the 
•jmnt  of  Hydra  east  and  west?  History  of  Hydra ? 


URSA    MAJOR.  78 

Juno  was  unable  to  succeed  in  her  attempts  to  lessen  the  fame  of  Hercules.  The  con* 
queror  dipped  his  arrows  in  the  gall  of  the  Hydra,  which  ever  after  rendered  the  wounds 
Inflicted  with  them  incurable  and  mortal. 

This  fable  of  the  many-headed  hydra  may  be  understood  to  mean  nothing  more  than 
that  the  marshes  of  Lerna  were  infested  with  a  multitude  of  serpents,  which  seemed  to 
multiply  as  fast  as  they  were  destroyed, 

TELESCOPIC  OBJECTS. 

\.  a  SRATERIS — A  star  with  two  very  distant  companions  in  the  base  of  the  cup ;  R.  A. 
tOh.  52m.  OOs  ;  Dec.  S.  17°  26'  9".  A.  4,  orange  tint;  B  8,  intense  blood  color ;  C  9,  p.-ile 
Hue. 

2.  y  CRATERIS— A  close  DOUBLE  STAR,  in  the  center  of  the  cup ;  R.  A.  llh.  16m.  54s. ; 
Dec.  S.  16°  48'  3";  A  4,  bright  white ;  B  14,  grey ,  with  a  star  of  the  llth  magnitude  fol- 
lowing, on  a  line  with  A.  B.  25'  distant. 

3.  6  CRATERIS — A  star  with  a  very  distant  companion,  on  the  cup,  midway  between 
Alphard  and  Spica,  but  a  little  south  of  the  line  joining  them;  R.  A.  llh.  llm.  21s.; 
Dec.  S.  13°  54'  8".     A  3^,  pale  orange ;  B  11,  pale  blue— other  small  stars  in  the  field. 

4.  a  HYDRJS  (Cor  Hydrce,)—K  bright  star  in  the  heart  of  Hydra  with  a  distant  com- 
panion ;  R.  A.  .th.  19m.  44s. ;  Dec.  S.  7°  58'  1".    A  2,  orange  tint;  B  10,  pale  green. 

5.  <5  HYDR.E— A  star  with  a  distant  companion  in  the  head  of  Hydra;   R.  A.  8h.  29m. 
14s. ;  Dec.  N.  6"  15'  5".    A  4,  light  topaz ;  B  9,  livid— several  other  stars  in  the  field. 

6.  e  HYDRJS— A  double  star  in  the  head ;  R.  A.  8h.  38m.  18s. ;  Dec.  N.  7°  00'  2'.    A  4, 
pale  yellow;  B  8J6,  purple. 

7.  A  PLANETARY  NEBULA  in  the  middle  of  the  body;   R.  A.  lOh.  17m.  Ols. ;  Dec.  S.  II* 
50'  6";  greyish  white. 


CHAPTER  VII. 

CONSTELLATIONS    ON   THE    MERIDIAN   IN   MAY. 

UKSA  MAJOR  (THE  GREAT  BEAR).— MAPS  IV.  AND  VI. 

142.  URSA  MAJOR  is  situated  between  Ursa  Minor  on  the  north, 
and  Leo  Minor  on  the  south.     It  is  one  of  the  most  noted  and 
conspicuous  in  the  northern  hemisphere.     It  has  been  an  object 
of  universal  observation  in  all  ages  of  the  world. 

The  priests  of  Belus  and  the  Magi  of  Persia,  the  shepherds  of  Chaldea,  and  the  Phoa- 
nician  navigators,  seem  to  have  been  equally  struck  with  its  peculiar  outlines.  And  i{ 
is  somewhat  remarkable,  that  a  remote  nation  of  American  Aborigines,  the  Iroquois, 
and  the  earliest  Arabs  of  Asia,  should  have  given  to  the  very  same  constellation  the 
name  of  "  Great  Bear,"  when  there  had  probably  never  been  any  communication 
between  them;  and  when  the  name  itself  is  so  perfectly  arbitrary,  there  being  no  resem- 
blance whatever  to  a  bear,  or  to  any  other  animal. 

143.  It  is  readily  distinguished  from  all  others  oy  means  of  a 
remarkable  cluster  of  seven  bright  stars,  forming  what  is  fami- 
liarly termed  the  Dipper,  or  Ladle.     In  some  parts  of  England 
it  is  called  "  Charles'  Wain,"  or  wagon,  from  its  fancied  resem- 

TKLKSCOPIO  OBJECTS.— Alpha?  Gamma?  Delta?  Alpha  Hydrae?  Delta  Hydras? 
Eta  Hydra  ?  What  Nebula  ? 

'i42.  Describe  Ursa  Major?  What  remarkable  fact  as  to  its  name?  148.  How  dis- 
tinguished? What  other  names  for  the  Dipper  ?  What  remark  in  small  type  ? 


74  ASTRONOMY. 

r 

blance  to  a  wagon  drawn  by  three  horses  in  a  line.  Others  call 
ifc  the  Plough.  The  cluster,  however,  is  more  frequently  put  foi 
the  whole  constellation,  and  called  simply  the  Great  Bear. 

We  see  no  reason  to  reject  the  very  appropriate  appellation  of  the  shepherds,  for  the 
resemblance  is  certainly  in  favor  of  the  Dipper ;  the  four  stars  in  the  square  forming  the 
bowl,  and  the  other  three  the  handle. 

144.  When  the  Dipper  is  on  the  meridian,  above  the  pole,  the 
bottom  lies  toward  us,  with  the  handle  on  the  right. 

Beiwtnascfi  is  a  bright  star  of  the  2d  magnitude,  and  is  the 
first  in  the  handle.  The  second,  or  middle  star  in  the  handle  is 
Mizar,  T  distant  from  Benetnasch.  It  may  be  known  by  means 
of  a  very  minute  star  almost  touching  it,  called  Alcor. 

145.  The  third  star  in  the  handle  is  called  Alioth,  and  is  about 
4^-°  W.  of  Mizar.     Alioth  is  very  nearly  opposite  Shedir  in  Cas- 
siopeia, and  at  an  equal  distance  from  the  pole.     Benetnasch, 
Mizar,  and  Alioth  constitute  the  handle,  while  the  next  four  in 
the  square  form  the  bowl  of  the  Dipper. 

146.  Five  and  a  half  degrees  W.  of  Alioth  is  the  first  star  in 
the  top  of  the  Dipper,  at  the  junction  of  the  handle,  called 
Megrez  ;  it  is  the  smallest  and  middle  one  of  the  cluster,  and  is 
used  in  various  observations  both  on  sea  and  land  for  important 
purposes. 

When  Megrez  and  Caph  have  the  same  altitude,  and  are  seen  in  the  same  horizontal 
line  east  and  west,  the  polar  star  is  then  at  its  greatest  elongation  from  the  true  pole  of 
the  heavens ;  and  this  is  the  proper  time  for  an  observer  to  take  its  angle  of  elevation, 
in  order  to  determine  the  latitude,  and  its  azimuth  or  angle  of  declination,  in  order  to 
determine  the  magnetic  variation. 

147.  At  the  distance  of  4£°  S.  W.  of  Megrez  is  Phad,  the 
first  star  in  that  part  of  the  bottom  which  is  next  the  handle. 

The  stars  in  this  cluster  are  so  well  known,  and  may  be  so  easily  described  without 
reference  to  their  relative  bearings,  that  they  would  rather  confuse  than  assist  the 
student,  were  they  given  with  ever  so  much  accuracy.  The  several  bearings  for  this 
cluster  were  taken  when  Megrez  was  on  the  meridian,  and  will  not  apply  at  any  other 
time,  though  their  respective  distances,  will  remain  the  same. 

148.  At  the  distance  of  8°  W.  of  Phad,  is  the  westernmost 
star  in  the  bottom  of  the  Dipper  called  Merak.     The  bright  star 
5°  N.  of  it,  toward  the  pole,  is  called  Dubhe.     These  two,  are. 
by  common  consent,  called  the  Pointers,  because  they  always 
point  toward  the  pole ;  for,  let  the  line  which  joins  them  be  con- 
tinued in  the  same  direction  28 J °  further,  it  will  just  reach  the 
north  pole. 

The  names,  positions,  and  relative  distances  of  the  stars  in  this  cluster  should  be  well 

144.  How  is  the  handle  of  the  Dipper  situated,  when  the  Dipper  is  above  the  pole? 
Describe  Benetnasch?  Mizar?  How  known?  145.  Alioth?  Megrez?  Remar* 
respecting?  Phad?  Remark  in  small  print?  148.  Merak  and  Dubhe?  Constitute 
what?  Remark  respecting  the  names,  positions  and  distances  of  the  stars  in  Crsa 
Mujorf  Why  should  these  distances  be  well  understood?  • 


URSA    MAJOR.  75 

remembered,  as  they  will  be  frequently  adverted  to.  The  distance  of  Dubht,  or  tho 
Pointer  nearest  to  the  north  pole,  is  28;-'4*.  The  distance  between  the  two  upper  stars  iu 
the  Dipper  is  10°;  between  the  two  lower  ones  is  8°;  the  distance  from  the  brim  to  the 
bottom  next  the  handle,  is  4>t°;  between  Megrez  and  Alioth,  is  5J$° ;  between  Alioth 
and  Mizar,  4%°;  and  between  Mizar  and  Benetnasch,  7°. 

The  reason  why  it  is  important  to  have  these  distances  clearly  settled  in  the  mind  is, 
that  these  stars,  being  always  in  view,  and  more  familiar  than  any  other,  the  student 
will  never  fail  to  have  a  standard  measure  before  him,  which  the  eye  can  easily  make 
use  of  in  determining  the  distances  between  other  stars. 

149.  The  position  of  Megrez  in  Ursa  Major,  and  of  Caph  in 
Cassiopeia,  is  somewhat  remarkable.     They  are  both  in  the  equi- 
noctial colure,  almost  exactly  opposite  each  other,  and  equally 
distant   from   the   pole.     Caph  is  in  the  colure,  which  passes 
through  the  vernal  equinox,  and  Megrez  is  in  that  which  passes 
through  the  autumnal  equinox.     The  latter  passes  the  meridian 
at  9  o'clock,  on  the  10th  of  May,  and  the  former  just  six  months 
afterward,  at  the  same  hour,  on  the  10th  of  November. 

150.  Psi,  in  the  left  leg  of  Ursa  Major,  is  a  star  of  the  4th 
magnitude,  in  a  line  with  Megrez  and  Fhad,  distant  from  the 
latter  12|°.     A  little  out  of  the  same  line,  3°  farther,  is  another 
star  of  the  4th  magnitude,  marked  Epsilon,  which  may  be  dis- 
tinguished from  Psi,  from  its  forming  a  straight  line  with  the  two 
Pointers. 

151.  The  right  fore-paw,  and  the  two  hinder  ones,  each  about 
15°  from  the  other,  are  severally  distinguished  by  two  stars  of 
the   4th   magnitude,   between  1°   and  2°  apart.     These   three 
duplicate  stars  are  nearly  in  a  right  line,  20°  S.  of,  and  in  a 
direction  nearly  parallel  with  Phad  and  Dubhe,  and  are  the  only 
stars  in  this  constellation  that  ever  set  in  this  latitude. 

There  are  a  few  other  stars  of  equal  brightness  with  those  just  described,  but  amidst 
the  more  splendid  and  interesting  group  with  which  they  are  clustered,  they  seldom 
engage  our  observation. 

The  whole  number  of  visible  stars  in  this  constellation  is  S7 ;  of  which  five  are  of  tho 
2d,  two  of  the  3d,  and  about  twice  as  many  of  the  4th  magnitude. 

HISTORY. 

URSA  MAJOR  is  said  to  be  Calisto,  or  Helice,  daughter  of  Lycaon,  king  of  Arcadia.  She 
was  an  attendant  of  Diana,  and  mother  of  Areas,  by  Jupiter,  who  placed  her  among  the 
constellations,  after  the  jealousy  of  Juno  had  changed  her  into  a  bear. 

"  This  said,  her  hand  within  her  hair  she  wound, 
Swung  her  to  earth,  and  dragg'd  her  on  the  ground; 
The  prostrare  wretch  ii;ts  up  her  hand  in  prayer; 
Her  arms  grow  shaggy,  and  deform'd  with  hair, 
Her  nails  are  sharpen'd  into  pointed  claws, 
Her  hands  bear  half  her  weight,  and  turn  to  paws; 
Her  lips,  that  once  could  tempt  a  god,  begin 
To  grow  distorted  in  an  ugiy  grin  ; 


149.  What  said  of  Megrez  and  Caph?        150.  Of  Psi  and  Epsilon?        151.  How  QuJ 
the/?^  of  the  figure?     Number  of  stars  in  Ursa  Major?     Magnitudes? 

HHTOHY. — Who  was  Ursa  M;ijor  before  she  became  a  bear?     What  other  supposition 
How  are  the  two  bears  represented  by  the  I^yptians?     What  further  remarks V 

B.G.  4 


76  ASTRONOMY. 

And  lest  the  supplicating  brute  might  reach 
The  ears  of  Jove,  she  was  deprived  of  speech. 
******* 

How  did  she  fear  to  lodge  in  woods  alone, 

And  haunt  the  fields  and  meadows,  once  her  own  ! 

How  often  would  the  deep-mouth'd  dogs  pursue, 

Whilst  from  her  hounds  the  frighted  hunters  flew." — Ovid's  Met. 

«ome  suppose  that  her  son  Areas,  otherwise  called  Bootes,  was  changed  into  Ursa 
Minor,  or  the  Little  Bear.  It  is  well  known,  that  the  ancients  represented  both  thes" 
constellations  under  the  figure  of  a  wagon  drawn  by  a  team  of  horses ;  hence  the  appel« 
lution  of  Charles'  Wain,  or  wagon.  This  is  alluded  to  in  the  Phenomena  of  Aratus,  a 
Greek  poem,  from  which  St.  Paul  quotes  in  his  address  to  the  Athenians: — 
*'  The  one  call'd  Helix,  soon  as  day  retires, 

Observed  with  ease  lights  up  his  radiant  fires. 

The  other,  smaller,  and  with  feebler  beams, 

In  a  less  circle  drives  its  laz,y  teams ; 

But  more  adapted  for  the  sailor's  guide, 

Whene'er,  by  night,  he  tempts  the  briny  tide." 

In  the  Egyptian  planispheres  of  remote  antiquity,  these  two  constellations  are  repre- 
sented by  the  figures  of  bears,  instead  of  wagons;  and  the  Greeks,who  derived  most  of  th  M.- 
astronomical  symbols  from  the  Egyptians,  though  they  usually  altered  them  to  emblems 
of  their  own  history  or  superstition,  have,  nevertheless,  retained  the  original  form  of 
the  two  bears,  It  is  said  by  Aratus,  that  the  Phrenician  navigators  made  use  of  Ursa 
Minor  in  directing  their  voyages  :— 

"  Observing  this,  Phoenicians  plough  the  main :" 

while  the  Greeks  confined  their  observations  to  Ursa  Major. 

Some  imagine  that  the  ancient  Egyptians  arranged  the  stars  near  the  North  Pole, 
within  the  outlines  of  a  bear,  because  the  polar  regions  are  the  haunts  of  this  animal, 
and  also  because  it  makes  neither  extensive  journeys  nor  rapid  marches. 

At  what  period  men  began  to  sail  by  the  stars,  or  who  were  the  first  people  that  did 
BO,  is  not  clear;  but  the  honoris  usually  given  to  the  Phoenicians.  That  it  was  prac- 
ticed by  the  Greeks,  as  early  as  the  time  of  the  Trojan  war,  that  is,  about  1200  years 
B.  C.,  we  learn  from  Homer  ;  for  he  says  of  Ulysses,  when  sailing  on  his  raft,  that 

"  Placed  at  the  helm  he  sate,  and  mark'd  the  skies, 
Nor  closed  in  sleep  his  ever  watchful  eyes." 

It  is  rational  to  suppose  that  the  stars  were  first  used  as  a  guide  to  travellers  by  land, 
for  we  can  scarcely  imagine  that  men  would  venture  themselves  upon  the  sea  by  night, 
before  they  had  first  learned  some  safe  and  sure  method  of  directing  their  course  by 
land.  And  we  find,  according  to  Diodorus  Siculus,  that  travellers  in  the  sandy  plains  of 
Arabia  were  accustomed  to  direct  their  course  by  Vie  Bears. 

That  people  travelled  in  these  vast  deserts  at  night  by  observing  the  stars,  is  directly 
proved  by  this  passage  of  the  Koran : — "  God  has  given  you  the  stars,  to  be  guided  in 
the  dark,  both  by  land  and  by  sea." 

TELESCOPIC  OBJECTS. 

1.  a  URSA  MAJOEIS  (Diibhe,  one  of  the  pointers)— A.  fine  star  with  a  distant  compa- 
nion ;  R.  A.  lOh.  53m.  48s. ;  Dec.  N.  62°  36'  8".     A  1  ^,  yellow  ;  B  8,  yellow. 

2.  (3  URSA  MAJORIS  (Merafc) — A  bright  star  with  a  distant  companion ;  R.  A.  lOh.  52m. 
OS";  Dec.  N.  57°  14'  2".     A  2,  greenish  while ;  B  11,  pale  grey— other  stars  in  field. 

3.  y  URSA  MAJORIS  (Phad)—K  star  with  a  distant  companion  ;    R.  A.  lib.  45m.  23s.  ; 
Dec.  N.  54°  35'  1".    A  2,  topaz  yellow ;  B  9,  ashy  paleuess,  with  a  fine  group  of  stars  in 
the  field. 

4.  6  URSA  MAJORIS  (Megrez) — A  fine  star,  suspected  of  variability,  with  a  distant  com- 
panion;   R.  A.  12h.  07m.  28s.;  Dec.  N.  57°  55'  3".    A  3,  pale  yellow;   B9,  ash  colored, 
with  other  stars  in  field.  .   . 

5.  (,  URSA  MAJORIS  (Misar.)— A  splendid  double  star  in  the  middle  of  the  tail ;  R.  A. 
13h.  17m.  2Ss.;  Dec.  N.  55°  45' 8".    A  3,  brilliant  white ;  B  5,  pale  emerald.    Alcor  and 
other  stars  in  the  field.    Map  VIII.  Fig.  7. 

TKLESCOPIC  OBJECTS.— Alpha ?    Beta?     Gamma?    Delta?    Zeta?    Eta?    Iota?    Nu 
Wl  -it  nebula?    Which  shown  on  tie  map? 


COMA    BERENICES.  77 

6.  n  URSA  MAJORIS  (Benetnasch)—\  DOUBLE  STAR  in  the  tip  of  the  tail;  R.  A.  18h.41m. 
i.4s. ;  Dec.  N.  50°  06'  5".    A  2)6,  brilliant  white  ;  B  9,  dusky. 

7.  i  URSA  MAJORIS  (Al  KaphraK) — A  DOUBLE  STAR  in  the  right  fo  -e  paw ;  R.  A.  8h.  48m. 
14s. ;  Dec.  N.  48°  39' 9".    A  3 }£,  topaz  yellow;   B  13,  purple.    Sir  J.  Uerschel  supposed  A 
might  be  a  satellite,  shining  only  by  reflection. 

8.  v  URSA  MAJORIS — A  delicate  DOUBLE  STAR  in  the  left  hind  foot,  just  above  £  or 
El  Acola ;  R.  A.  llh.  09m.  49s. ;  Dec.  N.  30°  58'  0'.    A  4,  orange  tint ;  B  12,  cornelian  blue ; 
a  close  but  elegant  object. 

9.  A  beautiful  PLANETARY  NEBULA,  just  south  of  /3 ;  R.  A.  lOh.  23m.  45s. ;  Dec.  N.  54' 
20'  4*.    A  small,  well  denned  object,  bluish  white,  and  brightens  towards  the  center. 

10.  A  BRIGHT  NEBULA  in  the  right  fore  leg ;  R.  A.  9h.  10m.  54s.;  Dec.  N.  51°  40'  5".    Of  a 
pale  creamy  whiteness,  with  several  bright  stars  in  the  northern  part  of  the  field. 
Nebula  large,  elliptical  and  nucleated. 

11.  A  bright-class  ROUND  NEBULA  above  the  Bear's  ear  ;  R.  A.  9h.  34m.  32s.  ;  Dec.  N.  78* 
01'  2".    Several  stars  in  field,  of  9th  to  J2th  magnitude. 

12.  A  FINE  OVAL  NEBULA  in  the  ear ;  R.  A.  9h.  42m.  10s. ;  Dec.  N.  69°  51'  8*. 

13.  A  LARGE  MILK-WHITE  NEBULA  on  the  body,  about  1°  south  of  ft  or  Merak  ;  R.  A.  llh. 
02m.  02s. ;  Dec.  N.  56°  31'  8". 

14.  A  LARGE  PLANETARY  NEBULA  on  the  Cank,  with  several  stars  in  the  field,  one  of 
which  is  pretty  close ;  R.  A.  llh.  05m.  24s. ;  Dec.  N.  55°  52'  9-    About  2°  to  the  S.  E.  of 
/3,  and  just  south  of  a  line  from  (3  to  y ;  a  singular  object,  circular,  uniform,  and  seem- 
ingly of  the  size  of  Jupiter.    W.  Uerschel  assigned  this  object  to  the  980th  order  of  dis- 
tance.   Map  VIII.,  Fig.  42. 

15.  A  BRIGHT-CLASS  NKBULA  in  a  poor  field,  behind  the  left  hind  leg,  one-third  the  dis- 
tance from  6  towards  Denebola;  R.  A.  llh.  58m.  51s.;  Dec.  N.  48°  57'  3".    Of  a  lucid 
white,  various  and  elongated.    Map  VIII.,  Fig.  43. 

16.  A  LARGE  WHITE  NEBULA  near  the  haunches ;  R.  A.  12h.  llm.  04s. ;  Dec.  N.  48°  11'  1\ 
A  noble-sized  oval,  with  a  bright  nucleus,  the  lateral  edges  better  defined  than  the  ends) 
Found  by  running  a  diagonal  line  across  the  square,  from  a  through  y,  and  about  7J$* 
beyond,  into  the  S.  E. 


COMA  BERENICES  (BERENICE'S  HAIR).— MAP  IV. 

152.  This  is  a  beautiful  cluster  of  small  stars,  situated  about, 
5°  E.  of  the  equinoctial  colure,  and  midway  between  Cor  Caroli 
on  the  northeast,  and  Denebola  on  the  southwest.     If  a  straight 
line  be  drawn  from  Benetnasch  through  Cor  Caroli,  and  pro- 
duced to  Denebola,  it  will  pass  through  it. 

153.  The  principal  stars  are  of  between  the  4th  and  5th  mag- 
nitudes.    According  to  Flamsted,  there  are  thirteen  of  the  4th 
magnitude,  and  according  to  others  there  are  seven  ;   but  the 
student  will  find  agreeably  to  his  map,  that  there  is  apparently 
but  one  star  in  this  group,  entitled  to  that  rank,  and  this  is 
situated  about  t°  S.  E.  of  the  main  cluster. 

Although  it  is  not  easy  to  mistake  this  group  for  any  other  in  the  same  region  of  the 
skies,  yet  the  stars  which  compose  it  are  all  so  small  as  to  be  rarely  distinguished  in  tho 
full  presence  of  the  moon.  The  confused  lustre  of  this  assemblage  of  small  stars  some- 
what resembles  that  of  the  Milky  Way. 

152  Describe  Coma  Berenices?  How  find  it?  158.  Its  principal  «tars,  their  numbct 
&c.?  What  remark  in  fine  print? 


78  ASTRONOMY. 

154.  The  whole  number  of  stars  in  this  constellation  is  43  ; 
its  mean  right  ascension  is  185°.  It  consequently  is  on  tho 
meridian  the  13th  of  May. 

"  Is  ow  behold 

The  glittering  maze  or  Berenice's  Hair; 
Forty  the  stars ;  but  such  as  seem  to  kisa 
Ihejfen0fo#  ti-essts  with  a  lambent  fire, 
Four  to  the  telescope  alone  are  seen." 

HISTORY. 

Berenice  was  of  royal  descent,  and  a  lady  of  great  beauty,  who  married  Ptolemy  Soter, 
or  Evergetes,  one  of  the  kings  of  Egypt,  her  own  brother,  whom  she  loved  with  much 
tenderness.  When  he  was  going  on  a  dan^vi'ous  expedition  against  the  Assyrians,  shs 
vowed  to  dedicate  her  hair  to  the  goddess  of  beauty,  if  he  returned  in  safety.  Some 
time  after  the  victorious  return  of  her  husband,  Evergetes,  the  locks,  which,  agreeably 
to  her  oath,  she  had  deposited  in  the  temple  of  Venus,  disappeared.  The  king  expressed 
great  regret  at  the  loss  of  what  he  so  much  prized  ;  whereupon  Conon,  his  astronomer, 
publicly  reported  that  Jupiter  had  taken  away  the  queen's  locks  from  the  temple  and 
placed  them  among  the  stars. 

"  There  Berenice's  locks  first  rose  so  bright, 

The  heavens  bespangling  with  dishevelled  light." 

Conon  being  sent  for  by  the  king,  pointed  out  this  constellation,  saying,  "  There  behold 
the  locks  of  the  queen."  This  group  being  among  the  unformed  stars  until  that  time, 
end  not  known  as  .1  constellation,  the  king  was  satisfied  with  the  declaration  of  the 
astronomer,  and  the  queen  became  reconciled  to  the  partiality  of  the  gods. 

Callimachus,  a  historian  and  poet,  who  flourished  long  before  the  Christian  era,  has 
these  lines  as  translated  by  Tytler : — 

"Immortal  Conon,  blest  with  skill  divine, 
Amid  the  sacred  skies  beheld  me  shine: 
E'en  me,  the  beuuieoiix  hitir,  that  lately  shed 
Refulgent  beams  from  Berenice''*  head  ; 
The  luck  she  fondly  vowed  with  lifted  »rms, 
Imploring  all  the  powers  to  save  from  inarms 
Her  dearer  lord,  when  from  his  bride  im  flew, 
To  wreak  stern  vengeance  on  the  Assyrian  crew." 

TELESCOPIC  OBJECTS. 

1.  A  TRIPLE  STAR,  between  the  tresses  and  Virgo's  northern  wing;  R.  A.  12h.  45m.  25s. , 
Dec.  N.  22°  07'  0".     A  5,  pale  yellow;    B,  indistinct;  C  10,  cobalt  blue.     About  7°  south, 
east  of  a  Berenices,  and  20°  west  of  Arcturus. 

2.  A  GLOBULAR  CLUSTER,  between  the  tresses  and  the  Virgin's  left  hand,  with  a  coarse 
pair  and  one  single  star  in  the  field;  R.  A.  11  h.  Oom.  03s. ;    Dec.  N.  19' 01  3".     A  brilliant 
mass  of  minute  stars  from  the  llth  to  the  15th  May;    compressed  at  center.    A  line 
through  (5  and  F  Virginia,  northward,  meeting  another  from  Arcturus  over  ty  Bootes,  falls 
upon  this  magnificent  object. 

8.  A  CONSPICUOUS  NKBn.A  between  the  tresses  and  the  virgin's  left  arm;  R.  A.  12h. 
48iu.  52s. ;  Dec.  N.  22°  84  2".  A  magnificent  object,  both  in  size  and  brightness,  witfc 
several  siuail  stars  in  the  field.  Elongated,  compressed  in  the  centre,  and  was  likened 
*y  Sir  Charles  Blagdon  to  a  "  black  eye."  Map  V1I1.,  Fig.  44. 


CORVUS  (THE  CEOW).— MAP  IY. 

155.  This  small  constellation  is  situated  on  the  eastern  part 
of  Hydra,  15°  E  of  the  Cup,  and  is  on  the  same  meridian  with 

154.  What  number  of  stars? 

HISTOKY.  -Who  was  Berenice?    Story  of  the  loss  of  her  hair,  4c.? 

TKI.E,->OOPIC  OBJKCTS. — What  triple  stars?    Cluster?    Nebula?     Point  out  on  the  Mao. 

155.  Where  ia  Corvus  situated?    Number  of  vidible  stars? 


CORVUS.  79 

Coma  Berenices,  but  as  far  S.  of  the  equinoctial  as  Coma  Bere- 
nices is  N.  of  it.  It  therefore  culminates  at  the  same  time,  on 
the  12th  of  May.  It  contains  nine  visible  stars,  including  three 
of  the  3d  magnitude,  and  two  of  the  4th. 

156.  This  constellation  is  readily  distinguished  by  means  of 
three  stars  of  the  3d  magnitude  and  one  of  the  4th,  forming  a 
trapezium  or  irregular  square,  the  two  upper  ones  being  about 
3|°  apart,  and  the  two  lower  ones  6°  apart. 

157.  The  brightest  of  the  two  upper  stars,  on  the  left,  is 
called  Algorab,  and  is  situated  in  the  E.  wing  of  the  Crow  ;  it 
has  nearly  the  same  declination  S.  that  the  Dog  Star  has,  and 
is  on  the  meridian  about  the  13th   of  May.     It  is  21£°  E.  of 
Alkes  in  the  Cup,  14^°  S.  W.  of  Spica  Yirginis,  a  brilliant  star 
of  the  1st  magnitude,  to  be  described  in  the  next  chapter. 

158.  Beta,  on  the  back  of  Hydra,  and  in  the  foot  of  the  Crow, 
is  a  star  of  the  3d  magnitude,  nearly  7°  S.  of  Algorab.     It  is 
the  brightest  of  the  two  lower  stars,  and  on  the  left.  The  right- 
hand  lower  one  is  a  star  of  the  4th  magnitude,  situated  in  the 
neck,  marked  Epsilon,  about  6°  W.  of  Beta,  and  may  be  known 
by  a  star  of  the  same  magnitude  situated  2°  below  it,  in  the  eye, 
and  called  AL  Chiba.     Epsilon  is  21|°  S.  of  the  vernal  equinox, 
and  if   a  meridian  should  be   drawn   from   the   pole   through 
Megrez,  and  produced  to  Epsilon  Corvi,  it  would  mark  the  equi- 
noctial colure. 

)59.  Gamma,  in  the  W.  wing,  is  a  star  of  the  3d  magnitude, 
3^-°  W.  of  Algorab,  and  is  the  upper  right-hand  on^  in  the 
square.  It  is  but  1°  E.  of  the  equinoctial  colure. 

10°  E.  of  Beta  is  a  star  of  the  3d  magnitude,  in  the  tail  of 
Hydra,  marked  Gamma  ;  these  two,  with  Algorab,  form  nearly 
a  right-angled  triangle,  the  right  angle  being  at  Beta. 

HISTORY. 

The  Crow,  it  is  said,  was  once  of  the  purest  white,  but  was  chan-ed  for  tale-bearing  to 
its  present  color.    A  fit  punishment  for  such  a  fault. 

*'The  raven  once  in  snowy  plumes  was  drest, 
White  as  the  whitest  dove's  unsullied  brcsst, 
Fair  as  the  guardian  of  the  capitol, 
Soft  ai  the  Swan  ;  a  large  and  lovely  fowl ; 
His  tongue,  his  prating  tongue,  had  changed  htm  quii/c, 
To  sooty  blackness  from  the  purest  white." 

According  to  Greek  fable  the  Crow  was  made  a  constellation  by  Apollo.     This  goj 
be.'ng  jealous  of  Coronis  (whom   he   tenderly  loved),   the   daughter   of  Phlegyas   and 


156.  How  is  it  found  ?  157.  What  said  of  Algorab  ?  153.  Of  Beta  ?  Epsilon  ? 
Al  Chiba?  What  said  of  the  Pole,  Megrez,  and  Epsilou?  159.  Of  Gamma?  What 
triangle  ? 

HISTORY. — Story  of  the  original  color  of  Corvus  ?  Greek  fable  of  the  origin  of  tb«- 
ccastellation  ?  What  other  account  ? 


80  ASTRONOMY. 

mother  of  JEsculapius,  sent  a  crow  to  watch  her  behavior;  the  bird  perceived  her  cri- 
minal partiality  for  Ischys  the  Thessalian,  and  immediately  acquainted  Apollo  with  hei 
conduct,  which  so  fired  his  indignation  that  he  lodged  an  arrow  in  her  breast,  and  killed 
l.er  instantly. 

"  T  le  god  was  wroth  ;  the  color  left  his  look, 

The  wreath  his  head,  the  harp  his  hand  forsook : 

The  silver  bow  and  feathered  shafts  he  took, 

And  lodged  an  arrow  in  the  tender  breast, 

That  had  so  often  to  his  own  been  prest." 
To  reward  the  crow,  he  placed  her  among  the  constellations. 

Others  say  that  this  constellation  takes  its  name  from  the  daughter  of  Corona?us, 
king  of  Phocis,  who  was  transformed  into  a  crow  by  Minerva,  to  rescue  the  maid  from 
the  pursuit  of  Neptune.  The  following,  from  an  eminent  Latin  poet  of  the  Augustan 
age,  is  her  own  account  of  the  metamorphosis  as  translated  into  English  verse  by  Mr. 
Addison : — 

"  For  as  my  arms  I  lifted  to  the  skies, 
I  saw  black  feathers  from  my  fingers  rise  ; 
I  strove  to  fling  my  garment  on  the  ground  ; 
My  garment  turned  to  plumes,  and  girt  me  round; 
My  hands  to  beat  my  naked  bosom  try ; 
Nor  naked  bosom  now,  nor  hands  had  !• 
Lightly  I  tripp'd,  nor  weary  as  before 
Sunk  in  the  sand,  but  skimm'd  along  the  shore  ; 
Till,  rising  on  my  wings,  I  was  preferr'd 
To  be  the  chaste  Minerva's  virgin  bird." 

TELESCOPIC  OBJECTS. 

1.  jtf  CORVI — A  fine  bright  star  nearly  midway  between  two  distant  companions.    A  2?$, 
ruddy  yellow ;  B  7,  greenish  yellow ;  C  8,  dull  grey,    ft  is  actually  the  lucida,  or  brightest 
star  of  the  constellation. 

2.  J  CORVI— A  DOUBLE  STAR  in  the  right  wing ;  R.  A.  12h.  21m.  85s. ;  Dec.  S.  15°  37'  04" 
A  3,  pale  yellow ;  B  8  Jg,  purple. 


VIRGO  (THE  VIRGIN).— MAP  IV. 

160.  This  is  the  sixth  sign,  and  seventh  constellation  in  the 
ecliptic.     It  is  situated  next  east  of  Leo,  and  about  midway 
between  Coma  Berenices  on  the  N.  and  Corvus  on  the  S.     It 
occupies  a  considerable   space   in   the   heavens,    and   contains, 
according  to  Flamsted,  one  hundred  and  ten  stars,  including  one 
of  the  1st,  six  of  the  3d,  and  ten  of  the  4th  magnitudes.     Its 
mean  declination  is  5°  N.,  and  its  mean  right  ascension  is  195°, 
Its  center  is  therefore  on  the  meridian  about  the  23d  of  May. 

The  sun  enters  the  sign  Virgo,  on  the  23d  of  August,  but  does  not  enter  the  con#tella~ 
tton  before  the  15th  of  September.  When  the  sun  is  in  this  sign,  the  earth  is  in  Pisces ; 
and  vice  versa. 

161.  Alpha,  or  Spica  Virgims,  in  the  ear  of  corn  which  the 
virgin  holds  in  her  left  hand,  is  the  most  brilliant  star  in  this 
constellation,  and  situated  nearly  15°  E.  N.  E.  of  Algorab  in 
the  Crow,  about  35°  S.  E.  of  Denebola,  and  nearly  as  far  S.  S. 

TELESCOPIC  OBJECTS. — Beta  ?    Delta  ? 

160.  Order  and  position  of  Virgo?  Extent?  Number  of  stars?  Magnitudes?  Mear 
declination  of  Virgo?  JJeicark  in  fine  print?  161.  What  said  of  Alpha,  or  Spica  Vir 


VIRGO.  81 

W.  of  Arcturus — three  very  brilliant  stars  of  similar  magnitude 
rhat  form  a  large  equilateral  triangle,  pointing  to  the  S.  Arc- 
turus and  Deuebola  are  also  the  base  of  a  similar  triangle  on 
the  north,  terminating  in  Cor  Caroli,  which,  joined  to  the  former, 
constitutes  the  Diamond  of  Virgo. 

162.  The  length  of  this  figure,  from  Cor  Caroli,  on  the  north, 
Co  Spica  Virginis  on  the  south,  is  50°.  Its  breadth,  or  shorter 
diameter,  extending  from  Arcturus  on  the  east  to  Denebola  on 
the' west,  is  35£°.  Spica  may  otherwise  be  known  by  its  soli- 
tary splendor,  there  being  no  visible  star  near  it  except  one  of 
the  4th  magnitude,  situated  about  1°  below  it,  on  the  left. 

The  position  of  this  star  in  the  heavens,  has  been  determined  with  great  exactness  for 
the  benefit  of  navigators.  It  is  one  of  the  stars  from  which  the  moon's  distance  is  taken 
for  determining  the  longitude  at  sea.  Its  situation  is  highly  favorab'e  for  this  purpose, 
is  it  lies  within  the  moon's  path,  and  little  more  than  2°  below  the  ear'h's  orbit. 

Its  right  ascension  being  199°,  it  will  come  to  our  meridian  at  9  o'clock  about  the  23th 
5f  May,  in  that  point  of  the  heavens  where  the  sun  is  at  noon  about  the  20th  of  October. 

]  63.  Beta,  called  also  Zavijava,  is  a  star  of  the  3d  magni- 
tude, in  the  shoulder  of  the  wing,  7^-°  W.  of  Eta,  with  which 
and  Gamma  it  forms  a  line  near  the  Earth's  orbit,  and  parallel 
to  it.  Beta,  Eta,  Gamma  and  Spica,  form  the  lower  and  longer 
side  of  a  large  spherical  triangle  whose  vertex  is  in  Beta. 

164.  Vindemiatrix,  is  a  star  of  the  3d  magnitude,  in  the  right 
arm,  or  northern  wing  of  Yirgo,  and.  is  situated  nearly  in  a 
straight  line  with,  and  midway  between  Coma  Berenices  and 
Spica  Yirginis.     It  is  19|-°  S.  W.  of  Arcturus,   and   about 
the  same  distance  S.  E.  of  Coma  Berenices,  and  forms  with  these 
two  a  large  triangle,  pointing  to  the  south.     It  bears  also  18° 
S.  S.  -E.  of  Deuebola,   and  comes  to  the  meridian  about  23 
minutes  before  Spica  Virginis. 

165.  Zeta,  is  a  star  of  the  3d  magnitude,  11^-°  j$T.  of  Spica, 
and  very  near  the  equinoctial.      Gamma,  situated  near  the  left 
side,  is  also  a  star  of  the  3d  magnitude,  and  very  near  the  equi- 
noctial.    It  is  13°  due  west  of  Zeta,  with  which  and  Spica  it 
forms  a  handsome  triangle.     Eta,  is  a  star  of  the  3d  magnitude 
"n  the  southern  wing,  5°  W.  of  Gamma,  and  but  2£°  E.  of  the 
autumnal  equinox. 

The  other  stars  in  this  figure  may  be  easily  traced  by  means  of  the  map.  About  13°  E. 
of  Spica,  there  are  two  stars  of  the  4th  magnitude,  3°  apart,  which  mark  the  foot  of  Virgo. 
These  two  stars  are  on  nearly  the  same  meridian  with  Arcturus,  and  culminate  nearly 
at  the  same  time.  The  lower  one,  marked  Lambda,  is  on  the  south,  and  but  8°  W.  of 
the  principal  star  in  Libra.  Several  other  stars  of  the  8d  magnitude  lie  scattered  about 
in  t-his  constellation,  and  may  be  traced  out  by  the  map. 

ginis?  Diamond?  162.  Length  of  Virgo?  Breadth?  How  may  Spica  be  known? 
Vote  in  fine  print?  163.  Describe  Beta?  What  triangle?  164.  V.ndematrLx ? 

165.  Zeta,  Gamma  and  Eta  ?     What  other  stars  and  how  found? 


82  ASTRONOMY. 

0 

"  Her  lovely  tresses  glow  with  starry  light; 
Stars  ornament  the  bracelet  on  her  hand  ; 
Her  vest  in  ample  fold,  glitters  with  stars: 
Beneath  her  snowy  feet  they  shine ;  her  eyes 
Lighten,  all  glorious,  with  the  heavenly  rays, 
toutjinit  the  star  which  crowns  the  golden  sheaf." 

HISTORY. 

According  to  the  ancient  poets,  this  constellation  represents  the  Virgin  Astrsea,  .he 
goddess  of  justice,  who  lived  upon  the  earth  during  the  golden  age  ;  but  being  off.-.id^d 
at  the  wickedness  and  impiety  of  mankind  during  the  brazen  and  iron  ages  of  the  world, 
she  returned  to  heaven,  and  was  placed  among  the  constellations  of  the  zodiac,  with  a 
pair  of  scales  (Libra)  in  one  hand  and  a  sword  in  the  other. 

Hesiod,  who  flourished  nearly  a  thousand  years  before  the  birth  of  our  Saviour,  and 
later  writers,  mention  four  ages  of  the  world ;  the  golden,  the  silver,  the  brazen,  and  the 
iron  age.  In  the  beginning  of  things,  say  they,  ail  men  were  happy,  and  all  men  were 
good;  the  earth  brought  forth  her  fruits  without  the  labor  of  man;  and  cares,  and 
wants,  wars  and  diseases,  were  unknown.  But  this  happy  state  of  tilings  did  not  last 
long.  To  the  golden  age,  the  silver  age  succeeded ;  to  the  silver  the  brazen  ;  and  to  the 
brazen,  the  iron.  Perpetual  spring  no  longer  reigned  ;  men  continually  quarreled  with 
each  other ;  crime  succeeded  to  crime  ;  and  blasphemy  and  murder  stained  the  hisiory 
of  every  day.  In  the  golden  age,  the  gods  did  not  disdain  to  mix  familiarly  with  the 
sons  of  men.  The  innocence,  the  integrity  and  brotherly  love  which  they  found  among 
us,  were  a  pleasing  spectacle  even  to  superior  natures;  but  as  mankind  degenerated, 
one  god  after  another  deserted  their  late  beloved  haunts;  Astraja  lingered  the  last;  but 
finding  the  earth  steeped  in  human  gore,  she  herself  new  away  to  the  celestial  regions. 

"  Victa  jacet  pietas;  et  virgo  caede  madentes 

Ultima  ccelestuin  terras  Astrasa  reliquit." 
Met.  Lib.  i.  v.  149. 
"Faith  flees,  and  piety  in  exile  mourns; 

And  justice  here  oppresb'd,  to  heaven  returns." 

Some,  however,  maintain,  that  Erigone  was  changed  into  the  constellation  Virgo.  The 
death  of  her  father  Icarus,  an  Athenian,  who  perished  by  the  hands  of  some  peasants, 
whom  he  had  intoxicated  with  wine,  caused  a  fit  of  despair,  in  which  Erigone  hung  her- 
self; and  she  was  afterward,  as  it  is  said,  placed  among  the  signs  of  the  zodiac.  She 
was  directed  by  her  faithful  dog  Maera  to  the  place  where  her  father  was  slain.  The 
first  bough  on  which  she  hung  herself  breaking,  she  sought  a  stronger,  in  order  to  effect 
her  purpose. 

"  Thus  once  in  Marathon's  impervious  wood, 
Erigone  beside  her  father  stood, 

When  hastening  to  discharge  her  pious  vows,  . 

She  loos'd  the  knot,  and  cull'd  the  strongest  boughs." 
LEWIS'  Statius,  B.  xi. 

The  famous  zodiac  of  Dendera,  as  we  have  already  noticed,  commences  with  the  sigi? 
Leo ;  but  another  zodiac,  discovered  among  the  ruins  at  Esne,  in  Egypt,  commences  with 
Virgo;  and  from  this  circumstance,  some  have  argued,  that  the  regular  precession  of 
the  equinoxes  established  a  date  to  this  at  least  2000  years  older  than  that  at  Dendera. 
The  discoveries  of  Champollion,  however,  render  it  probable  that  this  ancient  relic  of 
astrology  at  Esne  was  erected  during  the  reign  of  the  Emperor  Claudius,  and  conse- 
quently did  not  precede  the  one  at  Dendera  more  than  fourteen  years. 

Of  this,  however,  we  may  be  certain :  the  autumnal  equinox  now  corresponds  with 
the  first  degree  of  Virgo;  and,  consequently,  if  we  find  a  zodiac  in  which  the  summer 
solstice  was  placed  where  the  autumnal  equinox  now  is,  that  zodiac  carries  us  back  90* 
on  the  ecliptic;  this  divided  by  the  annual  precision  5054"  must  fix  the  date  at  about 
6450  years  ago.  This  computation,  according  to  the  chronology  of  the  Sacred  writings, 
carries  us  back  to  the  earliest  ages  of  the  human  species  on  earth,  and  proves,  at  least, 
that  astronomy  was  among  the  first  studies  of  mankind.  The  most  rational  way  of 
accounting  for  this  zodiac,  says  Jamieson,  is  to  ascribe  it  to  the  family  of  Noah ;  or  per- 
haps to  the  patriarch  himself,  who  constructed  it  for  the  benefit  of  those  who  should  live 
after  the  deluge,  and  who  preserved  it  as  a  monument  to  perpetuate  the  actual  state  of 
the  heavens  immediately  subsequent  to  the  creation. 
. 1 

HISTORY. — Account  of  the  poets?  Hesiod's  ace  rant?  What  other  supposition?  Wl.a 
Bodiitcs  mentioned,  and  what  calculations,  &c.  ? 


CANES    VENATICI.  83 


TELESCOPIC   OBJECTS. 

I.  a  VIRGINTS  (Spica) — A  splendid  star  with  a  minute  companion ;  R.  A.  13h.  16m.  47s. 
l>«c.  S-  10°  19  5".     A  1,  brilliant  flushed  white;  B  10,  bluish  tinge. 

2  j3  VIRGIXIS  (Zat'ijuri)— A  bright  star  with  a  small  companion  ;  R.  A.  llh.  42m.  22s. ; 
Dec.  N.  2°  4u'  0".  A  8>$,  pale  yellow  ;  B  11,  light  blue. 

3.  y  VIRGINIS — A  fine  BINARY  STAR  in  the  Virgin's  right  side ;  R.  A.  12h.  33m.  83s. ;  Dec. 
S.  0°  34'  3".     A  4,  silvery  white ;  B  4,  pale  yellow.     A  Binary  System  with  a  period  of 
about  157  years.     Map.  VIII.  Fig.  8. 

4.  ri  VIRGIXIS — A  star  with  a  distant  companion,  on  the  left  side,  about  17°  north-north- 
west of  Spica,  and  nearly  midway  between  y  and  e  Virginis  ;  R.  A.  12h.  47m.  33s. ;    Dec. 
N.  4°  16'  1'.     A  3^,  golden  yellow  ;  B  10^,  reddish  ;  several  small  stars  in  the  field. 

5.  e  VIRGIMS  (  Vendemiatrivc) — A  star  with  a  minute  distant  companion,  on  the  upper 
extremity  of  the  Virgin's  left  wing ;  R.  A.  T2h.  64m.  13s. ;  Dec.  11°  49  03".     A  3%,  bright 
yellow ;  B  15,  intense  blue.     This  last  color  on  so  small  an  object  is  very  striking. 

6.  A  TRIPLE  STAR  in  the  lower  part  of  the  southern  wing,  7°  northwest  of  Spica ;  R.  A. 
V3h.  Olni.  40s. ;  Dec.  S.  4"  41'  0'.    A  4^,  pale  white ;  B  9,  violet ;  C  10,  dusky. 

7.  A  LARGE,  BUT  RATHER  PALE  NEBULA,  between  Virgo's  left  wing  and  Leo's  tail ;  R.  A. 
12h.  06n-..  Ols.;  Dec.  N.  15'  47  02".     About  6^°  from  tf  Leonis,  towards  Arcturus,  on  the 
outskirts  of  a  vast  region  of  Nebula  in  the  Virgin's  wing.     It  is  elongated  in  the  directicn 
of  two  telescopic  stars. 

8.  A  LONG  PALE-WHITE  NEBULA,  among  telescopic  stars,  on  the  upper  part  of  the  Vir- 
gin's left  wing;  R.  A.  12h.  ()7in.  37s. ;  Dec.  N.  14"  02'  08".     Situated  one-third  of  the  way 
from  /3  Leonis  to  e  Virginis,  on  the  border  of  the  vast  nebulous  region  in  Virgo.     A 
curious  object  in  the  shape  of  a  weaver's  shuttle. 

9.  A  LUCID  WHITE  ELLIPTICAL  NEBULA,  between  the  Virgin's  right  elbow  and  the  Crow ; 
R.  A.  J2h.  31m.  40s. ;  Dec.  S.  10°  43'  07".     Map  VIII.,  Fig.  45. 

10.  A  DOUBLE  NEBULA  in  the  center  of  Virgo's  left  wing;  R.  A.  12h.  35m.  33s. ;  Dec.  N. 
12°  26'  01".     It  is  5"  west  of  Vendemiatrix,  toward   Regulus,  in  a  wonderful  nebulous 
region.     Map  VIII.,  Fig.  46,  shows  it  on  the  right,  with  two  other  nebulae,  and  several 
stars  in  the  figure. 

II.  A  PALE  ELLIPTICAL  NEBULA,  in  the  middle  of  the  left  wing;   R.  A.  12h.  44m.  50s., 
Dec.  N.  12"  05'  09".    It  looks  like  a  paper  kite,  under  an  ar.ch  formed  by  three  telescopic 
stars.    Map.  VIII.,  Fig.  47. 

12.  A  WONDFRFUL  NEBULOUS  REGiox,  about  2^"  from  north  to  south,  and  3"  from  east  to 
west,  is  found  on  the  left  wing.  It  includes  several  of  the  objects  described.  For  a 
arawing  of  this  remarkable  field,  see  Map  VIII.,  Fig.  48. 


CANES  YENATIOI  (THE  GREYHOUNDS).— MAP  IV. 

166.  This  modern  constellation,  embracing  two  in  one,  was 
made  by  Hevelius  out  of  the  unformed  stars  of  the  ancients 
which  were  scattered  between  Bootes  on  the  east,  and  Ursa 
Major  on  the  west,  and  between  the  handle  of  the  Dipper  on  the 
north,  and  Coma  Berenices  on  the  south. 

These  Hounds  are  represented  on  the  celestial  sphere  as  being  in  pursuit  of  the  Great 
Bear,  which  Bootes  is  hunting  round  the  pole  of  heaven,  while  heliolds  in  his  hand  the 
leash  by  which  they  are  fastened  together.  The  northern  one  is  called  Juttnim,  and 
the  southern  one,  Cluira. 


TELESCOPIC  OBJECTS.— Alpha?  Beta?  Gamma?  Delta?  Epsilon?  What  triple  star f 
Nebula?  Point  out  on  the  map. 

166.  Situation  of  Canes  Venatici  ?  By  whom  formed  ?  How  represented  ?  Nameo  of 
*ie  hounds  ? 

4* 


84  ASTRONOMY. 

167.  The  stars  in  this  group  are  considerably  scattered,  and 
are  principally  of  the  5th  and  6th  magnitudes  ;  of  the  twenty- 
five  stars  which  it  contains,  there  is  but  one  sufficiently  large  to 
engage  our  attention.  Cor  Caroli  or  CharkJ  Heart,  so  named 
by  Sir  Charles  Scarborough,  in  memory  of  King  Charles  the 
First,  is  a  star  of  the  3d  magnitude,  in  the  neck  of  Chara,  the 
southern  Hound. 

When  on  the  meridian,  Cor  Caroli  is  17%"  directly  S.  of  Alioth,  the  third  star  in  the 
handle  of  the  Dipper,  and  is  so  nearly  on  the  same  meridian  that  it  culminates  only  one 
minute  and  a  half  after  it.  This  occurs  on  the  20th  of  May. 

A  line  drawn  from  Cor  Caroli  through  Alioth  will  lead  to  the  N.  polar  star.  This  star 
may  also  be  readily  distinguished  by  its  being  in  a  straight  line  with,  and  midway  between 
Benetnasch,  the  first  star  in  the  handle  of  the  Dipper,  and  Coma  Berenices  ;  and  also  by 
the  fact  that  when  Cor  Caroli  is  on  the  meridian,  Denebola  bears  28°  S.  W.  and  Arcturus 
26°  S.  E.  of  it,  forming  with  these  two  stars  a  very  large  triangle,  whose  vertex  is  at  the 
north ;  it  is  also  at  the  northern  extremity  of  the  large  Diamond  already  described. 

The  remaining  stars  in  this  constellation  are  too  small  and  too  much  scattered  to  excite 
our  interest. 

TELESCOPIC    OBJECTS. 

1  A  DOUBLE  STAR  near  Chara's  mouth ;  R.  A.  12h.  08m.  06s. ;  Dec.  N.  41°  33'  01".  A  6, 
yellow;  B  9,  blue.  It  is  about  9°  south  of  Cor  Caroli,  and  one-third  of  the  distance 
between  that  star  and  d  Leonis.  Map  VIII.,  Fig.  10. 

2.  A  MAGNIFICENT  CLUSTER,  between  the  southern  Hound  and  the  knee  of  Bootes;  R.  A. 
13h.  34m.  45s.    A  splsndid  group,  supposed  to  contain  not  less  than  1,000  stars.    Map 
VIII.,  Fig.  49. 

3.  A  PAIR  OF  LUCID  WHITE  NEBULAE,  near  the  ear  of  the  northern  Hound ;  R.  A.  13h.  23m. 
06s. ;  Dec.  N.  48"  01'  07". 

4.  A  LARGE  BRIGHT  NEBULA,  2%°  north  by  west  of  Cor  Caroli ;  R.  A.  12h.  43m.  22s. ;  Dec. 
N.  41°  59'  07".    A  fin.i  pale-white  object,  compressed  toward  the  center,  and  with  several 
small  stars  in  the  field. 


CHAPTER  VIII. 

CONSTELLATIONS    ON   THE    MERIDIAN    IN   JUNE 

BOOTES  (THE  BEAK  DRIVER).— MAP  IV. 

1 68.  THE  BEAR-DRIVER  is  represented  by  the  figure  of  a  hunts- 
man in  a  running  posture,  grasping  a  club  in  his  right  hand,  and 
holding  up  in  his  left  the  leash  of  his  two  greyhounds,  Asterion 
and  Chara,  with  which  he  seems  to  be  pursuing  the  Great  Bear 
round  the  pole  of  the  heavens.  He  is  thence  called  Arcto- 
phylax,  or  the  "  Bear-Driver." 

167.  Describe  the  stars  in  this  group?     Cor  Caroli? 

TELESCOPIC  OBJECTS. — What  double  star  ?    Show  on  the  map  ?     Clusters?    Point  out  ou 
Che  map?     Nebulae? 

l<>8.  Describe  Bootes  ?    Why  called  the  P.ear-Driver* 


BOOTES.  »b 

169.  This  constellation  is  situated  between  Corona  Borealis 
on  the  east,  aid  Cor  Caroli,  or  the  Greyhounds,  on  the  west. 
It  contains  fifty-four  stars,  including  one  of  the  1st  magnitude, 
seven  of  the  3d,  and  ten  of  the  4th.     Its  mean  declination  is  20° 
N.,  and  its  mean  right  ascension  is  212°  ;  its  center  is  there- 
fore on  the  meridian  the  9th  of  June.     It  may  be  easily  distin- 
guished by  the  position  and  splendor  of  its  principle  star,  Arc- 
turns,  which  shines  with  a  reddish  luster,  Tery  much  resembling 
that  of  the  planet  Mars. 

170.  Arcturus  is  a  star  of  the  1st  magnitude,  situated  near 
the  left  knee,  26°  S.  E.  of  Cor  Caroli  and  Coma  Berenices,  with 
which  it  forms  an  elongated  triangle,  whose  vertex  is  at  Arc 
turus.     It  is  35^-°  E.  of  Denebola,  and  nearly  as  far  N.  of  Spica 
Virginis,  and  forms  with  these  two,  as  has  already  been  observed, 
a  large  equilateral  triangle.     It  also  makes,  with  Cor  Caroli  and 
Denebola,  a  large  triangle  whose  vertex  is  in  Cor  Caroli. 

A  great  variety  of  geometrical  figures  may  be  formed  of  the  stars  in  this  bright  region 
of  the  skies.  For  example :  Cor  Caroli  on  the  N.,  and  Spica  Virginis  on  the  S.,  constitute 
the  extreme  points  of  a  very  large  figure  in  the  shape  of  a  diamond ;  while  Denebola  on 
the  W.  and  Arcturus  on  the  E.,  limit  the  mean  diameter  <^t  the  other  points. 

171.  Arcturus  is  supposed  by  some  to  be  nearer  the  Earth 
than  any  other  star  in  the  northern  hemisphere. 

Five  or  six  degrees  S.  W.  of  Arcturus  are  three  stars  of  the  3d  and  4th  magnitudes, 
lying  in  a  curved  line,  about  2°  apart,  and  a  little  below  the  left  knee  of  Bootes ;  and 
about  7°  E.  of  Arcturus  are  three  or  four  other  stars  of  similar  magnitude,  situated  in 
the  other  leg,  making  a  larger  curve  N.  and  S. 

172.  Mirac,  in  the  girdle,  is  a  star  of  the  3d  magnitude,  10° 
N.  N.  E.  of  Arcturus,  and  about  11^°  W.  of  Alphacca,  a  star  in 
the  Northern  Crown.     Seginus,  in  the  west  shoulder,  is  a  star 
of  the  3d  magnitude,  nearly  20°  E.  of  Cor  Caroli,  and  about  the 
same  distance  N.  of  Arcturus,  and  forms  with  these  two,  a  right- 
angled  triangle,  the  right  angle  being  at  Seginus.     The  same 
star  forms  a  right-angled  triangle  with  Cor  Caroli  and  Alioth, 
in  Ursa  Major,  the  right  angle  being  at  Cor  Caroli. 

173.  Alkaturops,  situated  in  the  top  of  the  club,  is  a  star  of 
the  4th  magnitude,   about  10^-°  in  an  easterly  direction  from 
Seginus,  which  lies  in  the  left  shoulder  ;  and  about  4£°  S.  of 
Alkaturops  is  another  star  of  the  4th  magnitude,  in  the  club, 
near  the  east  shoulder,  marked  Delta.     Delta  is  about  9P  dis- 
tant from  Mirac,  and  7£°  from  Alphacca,  and  forms,  with  these 
two,  a  regular  triangle. 

1G9.  How  situated?  How  many  stars,  and  their  magnitude?  Declination?  How  dis- 
tinguished? 170.  Describe  Arcturus,  and  its  position  ?  What  triangles?  what  dia- 
mond? 171.  Supposed  nearness  of  Arcturus?  172.  Describe  Mirac  and  Seginus r 
'Vhat  triangles?  173.  Situation  and  magnitude  of  Alkaturops?  Of  Delta? 


Sty  ASTRONOMY. 

174.  Nekkar  is  a  star  of  the  3d  magnitude,  situated  in  the 
head,  and  is  about  6°  N.  E.  of  Seginus,  and  5 '  W.  of  Alkatu- 
rops ;  it  forms,  with  Delta  arid  Seginus,  nearly  a  right  angled 
triangle,  the  right  angle  being  at  Nekar. 

These  are  the  principal  stars  in  this  constellation,  except  the  three  stars  of  the  4th 
magnitude.situated  in  the  right  hand.  These  stars  may  be  known  by  two  of  them  being 
close  together,  and  about  5°  beyond  Benetnasch,  the  first  star  in  the  handle  of  the  Dip- 
per. About  6°  E.  of  Benetnasch  is  another  star  of  the  4th  magnitude,  situated  in  the 
arm  which  forms,  with  Benetnasch  and  the  three  in  the  hand,  an  equilateral  triangle. 

175.  The  three  stars  in  the  left  hand  of  Bootes,  the  first  in 
the  handle  of  the  Dipper,   Cor  Caroli,   Coma  Berenices,   and 
Denebola,  are  all  situated  nearly  in  the  same  right  line,  running 
from  northeast  to  southwest. 

"  Bootes  follows  with  redundant  light; 
Fifty-four  stars  he  boasts ;  one  guards  the  Bear, 
Thence  call'd  Arcturus,  of  resplendent  front, 
The  pride  of  the  first  order:  eight  are  veil'd, 
Invisible  to  the  unaided  eye." 

MANILIUS  thus  speaks  of  this  constellation  : — 

"  And  next  Bootes  comes,  whose  order'd  beams 
Present  a  figure  driving  of  his  teams. 
Below  his  girdle,  near  his  knees,  he  bears 
The  bright  Arcturus,  fairest  of  the  stars." 

176.  Arcturus  is  mentioned  by  name  ia  that  beautiful  passage 
in  Job,  already  referred  to,  where  the  Almighty  answers  ''out 
of  the  whirlwind,"  and  says  : — 

"  Canst  thou  the  sky's  benevolence  restrain, 
And  cause  the  Pleiades  to  shine  in  vain? 
Or,  when  Orion  sparkles  from  his  sphere,  • 
Thaw  the  cold  seasons  and  unbind  the  year? 
Bid  Mazzarotn  his  wonted  station  know, 
And  teach  the  bright  Arcturus  where  to  glow?" 

Young's  Paraphrase. 

HISTORY. 

The  ancient  Greeks  called  this  constellation  Lycaon — a  name  derived  from  Au/co?, 
which  signifies  a  wolf.  The  Hebrews  called  it  Caleb  Anubuch,  the  "  Barking  Dog ;" 
while  the  Latins,  among  other  names,  called  it  Cani*.  If  we  go  back  to  the  time  when 
Taurus  opened  the  year,  and  when  Virgo  was  the  fifth  of  the  zodiacal  signs,  we  shall 
find  that  brilliant  star  Arcturus,  so  remarkable  for  its  red  and  fiery  appearance,  corres- 
ponding with  a  period  of  the  year  as  remarkable  for  its  heat.  Pythagoras,  who  intro- 
duced the  true  system  of  the  universe  into  Greece,  received  it  from  (Enuphis,  a  priest  of 
On,  in  Egypt.  And  this  college  of  the  priesthood  was  the  noblest  of  the  east,  in  cultivat- 
ing the  studies  of  philosophy  and  astronomy.  Among  the  high  honors  which  Pharaoh 
conferred  on  Joseph,  he  very  wisely  gave  him  in  marriage  "  a  daughter  of  the  priest  of 
On."  The  supposed  era  of  the  book  of  Job,  in  which  Arcturus  is  repeatedly  mentioned, 
is  1518  B.  C. 

Bootes  is  supposed  by  some  to  be  Icarus,  the  father  of  Erigone,  who  was  killed  by 
shepherds  for  intoxicating  them.  Others  maintain  that  it  is  Erichthouius,  the  inventor 
of  chariots.  According  to  Grecian  fable,  as  well  as  later  authorities,  Bootes  was  the  son 
of  Jupiter  and  Calisto,  and  named  Areas.  Ovid  relates,  that  Juno,  being  incensed  at 
Jupiter  for  his  partiality  to  Calisto,  changed  her  into  a  bear,  and  that  her  son  Areas,  who 
became  a  famous  hunter,  one  day  roused  a  bear  in  the  chase,  and  not  knowing  that  it 

174.  Of  Nekkar?    Any  other  stars?        175.  What  said  of  three  stars  in  the  hand  of 
Bootes?        176.  What  star  in  Bootes  mentioned  in  the  Scriptures?    Poetic  quotation  ? 
HISTORY. — Greek  name  of  this  constellation?      Hebrew?      Grecian  fable?      Ovid'0 


BOOTES.  8? 

WAS  his  mother,  was  about  to  kill  her,  when  Jupiter  snatched  them  both  up  to  heaven 
and  placed  then  among  the  constellations.  Met.  b.  ii.  v.  49d-50S. 

u  But  now  her  son  had  fifteen  summers  told, 
Fierce  at  the  chase,  and  in  the  forest  bold  ; 
When  as  he  beat  the  woods  in  quest  of  prey, 
rle  chanced  to  rouse  his  mother  where  she  lay. 
She  knew  her  son,  and  kept  him  in  her  sight, 
And  fondly  gazed  :  the  boy  was  in  a  fright, 
And  aim'd  a  pointed  arrow  at  her  breast ; 
And  would  have  slain  his  mother  in  the  beast: 
But  Jove  forbade,  and  snatch'd  them  through  the  air 
In  whirlwinds  up  to  heaven,  and  fix'd  'em  there; 
Where  the  new  constellations  nightly  rise, 
And  add  a  luster  to  the  northern  skies." 

GatW*  Translation. 
LUCAN,  in  his  Pharsalia,  says— 

"  That  Brutus,  on  the  busy  times  intent, 
To  virtuous  Cato's  humble  dwelling  went, 
'Twas  when  the  solemn  dead  of  night  came  on, 
When  bright  Culixto,  with  her  nhining  xon, 
Now  half  that  circle  round  the  pole  had  run." 

This  constellation  is  called  Bootfs,  says  Cicero  (Nat.  D?o.  Lib.  ii.  41'),  from  a 
word  signifying  a  wagoner,  or  ploughman ;  and  sometimes  Arctvphylax  from 
words  signifying  bear-keeper  or  bear-driver. 

"  Arctophylax,  vulgo  qui  dicitur  esse  Bootes, 
Quod  quasi  temone  adjunctum  prae  se  quatit  Arctum." 

The  stars  in  this  region  of  the  skies  seem  to  have  attracted  the  admiration  of  almoct 
n.11  the  eminent  writers  of  antiquity.  Claudian  observes,  that 

"  Bootes  with  his  wain  the  north  unfolds; 
The  southern  gate  Orion  holds." 

And  Aratus,  who  flourished  nearly  SOO  years  before  Claudian,  says, 
"Behind,  and  seeming  to  urge  on  the  Bear, 
A"<Jtophylax,  on  enrth  Bootes  named, 
SheJs  o'er  the  Arctic  car  his  silver  light." 

This  is  the  poet  whom  St.  Paul  refers  to  when  he  tells  the  Athenians,  Acts  xvii.  23,  that 
"some  of  their  own  poets  have  said,  'Tow  yap  vat  yevo,  ecruev :'  For  we  are  also 
his  offspring."  These  words  are  the  beginning  of  the  5th  line  of  the  "Phenomena"  of 
Aratus,  a  celebrated  Greek  poem  written  it.  the  reign  of  Ptolemy  Philadelphus,  two 
thousand  one  hundred  years  ago,  and  afterward  translated  into  Latin  verse  by  Cicero. 
Aratus  was  a  poet  of  St.  Paul's  own  country.  The  apostle  borrows  again  from  the  same 
poet,  both  in  his  Epistle  to  the  Galatians,  and  to  Titus.  The  tfuf>jevt  of  the  poem  was 

5 rand  and  interesting:  hence  we  find  it  referred  to  in  the  writings  of  St.  Clement,  St. 
erome,  St.  Chrysostom,  (Ecumenius,  and  others.  As  this  poem  describes  the  nature  and 
motions  of  the  stars,  and  the  origin  of  the  constellations,  and  is,  moreover,  one  of  the 
oldest  compositions  extant  upon  this  interesting  subject,  the  author  has  taken  some 
pains  to  procure  a  Polyglot  copy  from  Germany r,  together  with  the  Axtronomicon  of 
Manilius,  and  some  other  works  of  similar  antiquity,  that  nothing  should  be  wanting  on 
his  part  which  could  impart  an  interest  to  the  study  of  the  constellations,  or  illustrate 
the  frequent  allusions  to  them  which  we  meet  with  in  the  Scriptures. 

Dr.  Doddridge  says  of  the  above  quotation,  that  "  these  words  are  well  known  to  be 
found  in  Aratus,  a  poet  of  Paul's  own  country,  who  lived  almost  8'>0  years  before  the 
apostle's  time;  and  that  the  same  words,  with  the  alteration  of  only  one  letter, mre  to 
be  found  in  the  Hymn  of  Cl, anthe*,  to  Jupiter,  the  Supreme  God;  which  is,  beyond 
comparison,  the  purest  and  finest  piece  of  n-titu-'dl  religion,  of  its  length,  which  I  know 
in  the  whole  wor'd  of  Pagan  antiquity;  and  which,  so  far  as  1  can  recollect,  contains 
nothing  unworthy  of  a  Christian,  or,  I  had  almost  said,  of  an  inspired  pen.  The  apostle 
might  perhaps  refer  to  Clfanth'H,  as  well  as  to  his  countryman  Aratus." 

Many  of  the  elements  and  fables  of  heathen  mythology  are  so  blended  with  the 

account?  Lucan  and  Cicero?  Claudian?  Aratus?  Who  was  Aratus?  What  remark 
able  quotation  ?  Remark  of  Doddridge  ?  What  other  passage  cited  by  St.  Paul  ?  Fronc 
whom  ? 


88  ASTRONOMY. 

Inspired  writings,  that  they  must  needs  be  studied,  more  or  less,  in  order  to  have  a  morr 
proper  understanding  of  numerous  passages  both  in  the  Old  and  New  Testament. 

The  great  apostle  of  the  Gentiles,  in  uttering  his  inspired  sentiments,  and  in  penning 
his  epistles,  often  refers  to  and  sometimes  quotes  verbatim  from  the  distinguished  writers 
who  preceded  him. 

Thus,  in  1  Cor.  xv.  33,  we  have  "  M?;  TrliavasOe'  'Qdetpovctv  rjdrj  XpTjaO'  o/ui'hiai 
•cot/cat.'  Be  not  deceived;  evil  communications  corrupt  good  manners;"  which  is  a 
flteral  quotation  by  the  apostle  from  the  Thais  of  Menander,  an  inventor  of  Greek 
comedy,  and  a  celebrated  Athenian  poet,  who  flourished  nearly  400  years  before  the 
apostle  wrote  his  epistle  to  the  Corinthians.  Thus  Paul  adopts  the  sentiment  of  the 
jomedian,  and  it  becomes  hallowed  by  "  the  divinity  that  stirred  within  him."  Tertul- 
;ian  remarks,  that  "  in  quoting  this,  the  apostle  hath  sanctified  the  poet's  sentiment." 

TELESCOPIC  OBJECTS. 

1.  a  Boons  (Arcturus)— A.  DOUBLE  STAR  ;  R.  A.  14h.  08m.  22s. ;  Dec.  N.  20"  00'  9".  A  1, 
A eddish  yellow;  B  11,  lilac. 

2.  /3  Boons  (Nfkka-r) — A  star  with  a  distant  companion  in  the  head  of  the  figure ;  R.  A- 
I4h.  55m.  55s. ;  Dec.  N.  41°  01'  5".    A  3,  golden  yellow :  B  11,  pale  grey. 

3.  6  Boons— A  star  with  a  distant  companion  in  the  left  shoulder ;  R.  A .  15h.  09m.  03s.; 
Dec.  N.  S3"  54' 9".    A  3J6,  pale  yellow;  B  8%,  light  blue. 

4.  e  BOOTIS  (Mirac)— A  DOUBLE  STAR  in  the  left  hip  ;  R.  A.  14h.  38m.  OOs. ;  Dec.  N.  27* 
45'  1".    A  3,  pale  orange  ;  B  7,  sea  green.    A  lovely  objects-colors  distinct,  and  strongly 
contrasted. 

5.  £,  BOOTIS — A  close  DOUBLE  STAR  on  the  left  leg ;  R.  A.  14h.  33m.  31s. ;  Dec.  N.  14°  25' 
1".    A  3J£,  bright  white ;  B  4%,  bluish  white. 

6.  77  BOOTIS  (Mufride) — A  star  with  a  distant  companion  on  the  right  leg ;  R.  A.  13h. 
47m.  04s. ;  Dec.  N.  19°  12'  0".    About  5%°  west  by  south  of  Arcturus.    A  3,  pale  yellow ; 
B  10  Jj,  lilac. 

7.  i  BOOTIS— A  DELICATE  TRIPLE  STAR  in  the  right  hand  (Map  VI.)  ;  R.  A.  14h.  10m.  80s.; 
Dec.  N.  52°  06'  4*.    A  and  B  4%,  pale  yellow ;  C  8,  creamy  white. 

8.  £  BOOTIS— A  BINARY  STAR  on  the  left  knee ;  R.  A.  14h.  44m.  OOs. ;  Dec.  N.  19°  46'  1* 
A  3%,  orange  ;  B  6%,  purple.     Supposed  period  400  years. 

9.  A  RICH  GROUP  of  stars  in  the  vicinity  of  Arcturus,  and  surrounding  that  star.    May 
be  seen  with  small  telescopes.    Map  VIII.,  Fig.  50. 

10.  A  PALE  WHITE  NEBULA  in  a  nebulous  field,  5°  north  northeast  of  Alkaid ;  R.  A. 
i3h.  57m.  81s. ;  Dec.  N.  55°  08'  8".    About  5°  southeast  of  Mizar.    A  difficult  object 
except  with  a  good  instrument. 

11.  A  WHITE  ROUND  NEBULA  near  the  right  shoulder ;  R.  A.  14h.  llm.  44s. ;  Dec.  N.  87* 
14'  4".    Pale,  except  at  the  center — telescopic  stars  in  the  field. 


JSTOCTA  (THE  OWL).— MAP  IV. 

iTt.  This  small  asterismis  situated  between  the  feet  of  Yirgo, 
on  the  north,  and  the  tail  of  Hydra,  on  the  south.  It  has  but  few 
stars,  and  those  only  of  the  5th  and  6th  magnitudes.  It  is  often 
omitted  altogether  from  the  constellations. 


CENTAURUS  (THE  OENTAUE).— MAP  IY.  AND  VII. 

178.  This  fabulous  monster  is  represented  by  the  figure  of  a 
man,  terminating  in  the  body  of  a  horse,  holding  a  wolf  at  arm't 

TKLESCOPIC  OBJECTS. — Alpha?     Beta'     Delta?     Epsilon?    Zeta?    Eta?     Iota?     Xif 
What,  rich  group?     Point  out  on  the  m;ip.    What  nebulae? 
177.  Describe  Nocta,  its  situation,  stars,  &c. 


CENTAURUS.  89 

length  in  one  hand,  while  he  transfixes  its  body  with  a  spear  in 
the  other. 

Although  this  constellation  occupies  a  large  space  in  the 
southern  hemisphere,  yet  it  is  so  low  down  that  the  main  part 
ol'  it  cannot  be  seen  in  our  latitude.  It  is  situated  south  of 
Spica  Yirginis,  with  a  mean  declination  of  50°.  It  contains 
thirty-five  stars,  including  two  of  the  1st  magnitude,  one  of  the 
2d,  and  six  of  the  3d  ;  the  brightest  of  which  are  not  visible  in 
the  United  States. 

179.  Theta  is  a  star  of  between  the  2d  and  3d  magnitude,  in 
the  east  shoulder,  and  may  be  seen  from  this  latitude,  during  the 
month  of  June,  being  about  27°  S.  by  E.  from  Spica  Yirginis, 
and  12°  or  13°  above  the  southern  horizon.  It  is  easily  recog- 
nized in  a  clear  evening,  from  the  circumstance  that  there  is  no 
other  star  of  similar  brightness  in  the  same  region,  for  which  it- 
can  be  mistaken.  It  is  so  nearly  on  the  same  meridian  with 
Arcturus  that  it  culminates  but  ten  minutes  before  it. 

Iota  is  a  star  of  between  the  4th  and  5th  magnitude,  in  the  west  shoulder,  9j£*  W.  of 
Theta.  It  is  about  26°  almost  directly  south  of  Spica  Virginis,  and  is  on  the  meridian 
nearly  at  the  same  time. 

Mu  and  Nu  are  stars  of  the  4th  magnitude,  in  the  breast,  very  near  together,  and  form 
a  regular  triangle  with  the  two  stars  in  the  shoulders. 

A  few  degrees  north  of  the  two  stars  in  the  shoulders,  are  four  small  stars  in  the  head. 
The  relative  position  of  the  stars  in  the  head  and  shoulders  is  very  similar  to  that  of  the 
stars  in  the  head  and  shoulders  of  Orion. 

HISTORY. 

Centaurs,  in  mythology,  were  a  kind  of  fabulous  monsters,  half  men  and  half  horses. 
This  fable  is,  hrwever,  differently  interpreted;  some  suppose  the  Centaurs  to  have  been 
a  body  of  shepherds  and  herdsmen,  rich  in  cattle,  who  inhabited  the  mountains  of  Arca- 
dia, and  to  whom  is  attributed  the  invention  of  pastoral  poetry.  But  Plutarch  and  Pliny 
are  of  opinion  that  such  monsters  have  really  existed.  Others  say,  that  under  the  reign 
of  Ixion,  king  of  Thessaly,  a  herd  of  bulls  ran  mad,  and  ravaged  the  whole  country, 
rendering  the  mountains  inaccessible  ;  and  that  some  young  men,  who  had  found  the  art 
of  taming  and  mounting  horses,  undertook  to  expel  these  noxious  animals,  which  they 
pursued  on  horseback,  and  thence  obtained  the  appellation  of  Centaurs. 

This  success  rendering  them  insolent,  they  insulted  the  Lapithse,  a  people  of  Thessaly ; 
and  because,  when  attacked,  they  fled  with  great  rapidity,  it  was  supposed  that  they 
were  half  horses  and  half  men ;  men  on  horses  being  at  that  period  a  very  uncommon 
light,  and  the  two  appearing,  especially  at  a  distance,  to  constitute  but  one  animal.  So 
the  Spanish  cavalry  at  first  seemed  to  the  astonished  Mexicans,  who  imagined  the  horse 
nnd  his  rider,  like  the  Centaurs  of  the  ancients,  to  be  some  monstrous  animal  of  a  ter- 
rible~form. 

The  Centaurs,  in  reality,  were  a  tribe  of  Lapithae,  who  resided  near  Mount  Pelion,  and 
first  invented  the  art  of  breaking  horses,  as  intimated  by  Virgil. 

"  The  Lapithas  to  chariots  add  the  state 
Of  bits  and  bridles  ;  taught  the  steed  to  bound 
To  turn  the  ring,  and  trace  the  mazy  ground; 
To  stop,  to  fly,  the  rules  of  war  to  know; 
To  obey  the  rider,  and  to  dare  the  foe." 

Centaurus  is  so  low  down  in  the  south  that  it  would  be  of  no  service  to  describe  its  tele 
scopic  objects. 

ITS.  How  is  Centaurys  represented  ?  Its  situation?  Number  of  stars,  & 3.?  179.  Theta 
Iota,  Mu,  Nu,  Ac.? 

HISTORY. — What  was  Centaurus?    Different  opinions? 


93  ASTRONOMY. 


LUPUS  (THE  WOLF).— MAPS  V.  AND  VII. 

180.  This  constellation  is  situated  next  east  of  the  Centaur, 
and  south  of  Libra  ;  arid  is  so  low  down  in  the  southern  hemi- 
sphere, that  only  a  few  stars  in  the  group  are  visible  to  us.  It 
contains  twenty-four  stars,  including  three  of  the  3d  magnitude, 
and  as  many  of  the  4th  ;  the  brightest  of  which,  when  on  the 
meridian,  may  be  seen  in  a  clear  evening,  just  above  the  southern 
horizon.  Their  particular  situation,  however,  will  be  better 
traced  out  by  reference  to  the  map  than  by  written  directions. 

The  most  favorable  time  for  observing  this  constellation  is 
toward  the  latter  end  of  June. 

HISTORY. 

This  constellation,  according  to  fable,  is  Lycaon,  king  of  Arcadia,  who  lived  about CGOO 
years  ago,  and  was  changed  into  a  wolf  by,  Jupiter,  because  he  offered  human  victims  on 
the  altars  of  the  god  Pan.  Some  attribute  this  metamorphosis  to  another  cause.  The 
Bins  of  mankind,  as  they  relate,  had  become  so  enormous,  that  Jupiter  visited  the  earth 
to  punish  its  wickedness  and  impiety.  He  came  to  Arcadia,  where  he  was  announced  as 
li  god,  and  the  people  began  to  pay  proper  adoration  to  his  divinity.  Lycaon,  however, 
who  used  to  Sacrifice  all  strangers  to  his  wanton  cruelty,  laughed  at  the  pious  prayers 
of  his  subjects,  and  to  try  the  divinity  of  the  god,  served  up  human  flesh  on  his  table. 
This  impiety  so  offended  Jupiter,  that  he  immediately  destroyed  the  house  of  Lycaon. 
and  changed  him  into  a  wolf. 

"  Of  these  he  murders  one ;  he  boils  the  flesh, 

And  lays  the  mangled  morsels  in  a  dish ; 

Some  part  he  roasts ;  then  serves  it  up  so  dress'd, 

And  bids  me  welcome  to  his  human  feast. 

Moved  with  disdain,  the  table  I  o'erturned, 

And  with  avenging  flames  the  palace  burn'd. 

The  tyrant  in  a  fright  for  shelter  gains 

The  neighboring  fields,  and  scours  along  the  plains: 

Howling  he  fled,  and  fain  he  would  have  spoke, 

But  human  voice  his  brutal  tongue  forsook. 

His  mantle,  now  his  hide,  with  ragged  hairs, 

Cleaves  to  his  back  :  a  famish'd  face  he  bears ; 

His  arms  descend,  his  shoulders  sink  away 

To  multiply  his  legs  for  chase  of  prey: 

He  grows  a  wolf."—  Ovid.  M<t.  B.  i. 

TELESCOPIC    OBJECTS. 

1.  a  Lcpr — A  star  with  a  distant  companion,  in  the  tail  of  Lupus ;  R.  A.  5h   o**>ra, 
40s. ;  Dec.  S.  17°  56  5".     A  3,^,  pale  yellow  ;    B  9%,  grey.     To  find,  draw  a  line  fr^ra  e 
the  central  star  of  Orion's  belt,  through  6  and  its  nebulous  patch  on  the  sword,  as  low 
down,  and  Sirius,  and  you  meet  a  Lupi. 

2.  (3  LCHI— A  DOUBLE  STAR;  R.  A.  5h.  21m.  23s. ;  Dec.  S.  20°  53'  5".     A  4,  deep  yel- 
iow;  B  11,  blue. 

S.  y  LCPI— A  wide  TRIPLK  STAR  in  a  barren  field;  R.  A.  5h.  87m.  48s.;  Dec.  2C* 
3l>'  2".  A  4,  light  yellow  ;  B  6%,  pale  green  ;  C  18,  dusky.  A  line  from  (5  Orionis  through 
the  second  cluster,  and  carried  16°  beyond,  falls  upon  it. 

4.  A  bright  STELLAR  NKBCLA,  of  a  milky  white  tinge  ;  R.  A.  5h.  17m.  50s.  Dec  S.  '24° 
89'  9".  A  fine  object  blazing  towards  the  centre. 


180.  Situation  of  Lupus ?     Number  and  magnitude  of  its  stars?    Best  time  to  observe? 
HISTORY. — What  was  Lupus  originally?    Why  changed  and  by  whom?    Described  by 
What  poet? 
TELESCOPIC  OBJECTS.— Alpha?    Beta?    Gamma?    WhatNebulu? 


LIBRA.  91 


LIBRA  (THE  SCALES).— MAP  IV.  AND  Y. 

181.  This  is  the  seventh  sign,  and  eighth  constellation,  from 
the  vernal  equinox,  and  is  situated  in  the  Zodiac,  next  east  of 
Virgo. 

The  sun  enters  this  sign,  at  the  autumnal  equinox,  on  the  23d 
of  September  ;  but  does  not  reach  the  constellation  before  the 
21th  of  October.  When  the  sun  enters  the  sign  Libra,  the 
days  and  nights  are  equal  all  over  the  world,  and  seem  to 
observe  a  kind  of  equilibrium,  like  a  balance. 

When,  however,  it  is  said  that  the  vernal  and  autumnal  equinoxes  are  in  Aries  and 
Libra,  and  the  tropics  in  Cancer  and  Capricorn,  it  must  be  remembered  that  the  xiyiK> 
Aries  and  Libra,  Cancer  and  Capricorn,  and  not  the  constellations  of  these  names,  are 
meant:  for  the  equinoxes  are  now  in  the  constellations  Pisces  and  Virgo,  and  the  tropics 
in  Gemini  and  Sagittarius  ;  each  constellation  hating  gone  forward  one  isign  in.  tke 
ecliptic. 

About  22  centuries  ago,  the  conMellution  Libra  coincided  with  the  sign  Libra;  but 
having  advanced  30°  or  more  in  the  ecliptic,  it  is  now  in  the  sign  Scorpio,  and  the  con- 
stellation Scorpio  is  in  the  sign  Sagittarius,  and  so  on. 

While  Aries  is  now  advanced  a  whole  sign  above  the  equinoctial  point  into  north  decli- 
nation, Libra  has  descended  as  far  below  it  into  south  declination. 

182.  Libra  contains  fifty-one  stars,  including  two  of  the  2d 
magnitude,  two  of  the  3d,  and  twelve  of  the  4th.     Its  mean 
declination  is  8°  south,  and  its  mean  right  ascension  226°.     Its, 
center  is  therefore  on  the  meridian  about  the  22d  of  June. 

It  may  be  known  by  means  of  its  four  principal  stars,  forming 
a  quadrilateral  figure,  lying  northeast  and  southwest,  and 
having  its  upper  and  lower  corners  nearly  in  a  line  running  north 
and  south.  The  two  stars  which  form  the  N.  E.  side  of  the 
square,  are  situated  about  7°  apart,  and  distinguish  the  Northern 
Scale.  The  two  stars  which  form  the  S.  W.  side  of  the  square 
are  situated  about  6°  apart,  and  distinguish  the  Southern  Scale. 

Zubeneschamnli,  in  the  Southern  Scale,  about  21°  E.  of  Spi"-a,  and  8°  E.  of  Lambda 
Virginis,  is  a  star  of  the  2d  magnitude,  and  is  situated  very  near  the  ecliptic,  about  42J^° 
E.  of  the  autumnal  equinox.  The  distance  from  this  star  down  to  Theta  Centauri  ia 
about  23°,  with  which,  and  Spica  Virginis,  it  forms  a  large  triangle,  on  tlie  right. 

Zubenelgr'nwbi,  the  uppermost  star  in  the  Northern  Scale,  is  also  of  the  2d  magnitude, 
9J^°  above  Zubeneschamali,  toward  the  northeast,  and  it  comes  to  the  meridian  about 
twenty-six  minutes  after  it,  on  the  23d  of  June.  Zubenelgemabi  is  the  northernmost  of 
the  four  bright  stars  in  this  figure,  and  is  exactly  opposite  the  lower  one,  which  is  11* 
south  of  it. 

Zubentuikrabi  is  a  star  of  the  3d  magnitude  in  the  Northern  Scale,  7°  S.  E.  of  Zubenel- 
gemabi, and  nearly  opposite  to  Zubeneschamali,  at  the  distance  of  11°  on  the  east. 
These  two  make  the  diagonal  of  the  square  east  and  west. 

Iota  is  a  star  of  the  4th  magnitude,  and  constitutes  the  souf  ernmost  corner  of  the 
square.  It  is  about  6°  S.  E.  of  Zubeneschamali,  and  11°  S.  of  Zuoenelgemabi,  with  which 
it  forms  the  other  diagonal  north  and  south. 

Zebenelffubi  is  a  star  of  the  3d  magnitude,  situated  below  the  Southern  Scale,  at  tho 

181.  Order  and  situation  of  Libra?  What  circumstance  suggesting  a  balance?  What 
remarks  respecting  the  distinction  between  the  xigns  and  the  constellations  ?  182.  Num- 
ber of  stars  in  Libra?  Its  mean  declination?  Right  ascension?  When  on  the  meri- 
dian? How  may  it  be  known?  Describe  the  four  stars.  Closing  remarks ? 


92  ASTRONOMY. 

distance  of  6°  from  Iota,  and  marks  the  southern  limit  of  the  Zodiac.  It  is  situated  In  a 
right  line  with,  and  nearly  midway  between  Spica  Virginia  and  Beta  Scorpionis  :  and 
comes  to  the  meridian  nearly  at  the  same  moment  with  Nekkar,  in  the  head  of  Bootes. 

The  remaining  btars  in  this  constellation  are  too  small  to  engage  attention. 

The  scholar,  in  tracing  out  this  constellation  in  the  heavens,  will  perceive  that  Lambda 
and  Mu,  which  lie  in  the  feet  of  Virgo  on  the  west,  form,  with  Zubeneschamali  and 
Zubenelgemabi,  almost  as  handsome  and  perfect  a  figure,  as  the  other  two  stars  in  the 
Balance  do  on  the  east. 

HISTORY. 

Virgo  was  the  goddess  of  justice,  and  Libra,  the  scales,  which  she  is  usually  repre- 
sented as  holding  in  her  left  hand,  are  the  appropriate  emblem  of  her  office. 

The  Libra  of  the  Zodiac,  says  Maurice,  in  his  Indian  Antiquities,  is  perpetually  seen 
upon  all  the  hieroglyphics  of  Egypt ;  which  is  at  once  an  argument  of  the  great  antiquity 
of  this  asterism,  and  of  the  probability  of  its  having  ueen  originally  fabricated  by  the 
astronoriical  sons  of  Misraim.  In  some  few  zodiacs,  Astrsca,  or  the  virgin  who  holds  the 
balance  in  her  hand  as  an  emblem  of  equal  justice,  is  not  drawn.  Such  are  the  zodiacs 
of  Esne  and  Dendera.  Humboldt  is  of  opinion,  that  although  the  Romans  introduced 
*his  constellation  into  their  zodiao  in  the  reign  of  Julius  Caesar,  still  it  might  have  been 
used  by  the  Egyptians  and  other  nations  of  very  remote  antiquity. 

It  is  generally  supposed  that  the  figure  of  the  balance  has  been  used  by  all  nations  to 
denote  the  equality  of  the  days  and  nights,  at  the  period  of  the  sun's  arriving  at  this 
sign.  It  has  also  been  observed,  that  at  this  season  there  is  a  greater  uniformity  in  th« 
temperature  of  the  air  all  over  the  earth's  surface. 

Others  affirm,  that  the  beam  only  of  the  balance  was  at  first  placed  among  the  stars, 
and  that  the  Egyptians  thus  honored  it  as  their  Nttometer,  or  instrument  by  which  they 
measured  the  inundations  of  the  Nile.  To  this  custom  of  measuring  the  waters  of  the 
Nile,  it  is  thought  the  prophet  alludes,  when  he  describes  the  Almighty  as  measuring 
the  waters  in  the  hollow  o/M-s  hand. — Isa.  xl.  12. 

The  ancient  husbandmen,  according  to  Virgil,  were  wont  to  regard  this  sign  as  indi 
eating  the  proper  time  for  sowing  their  winter  grain : — 

t  "  But  when  Astraea's  balance,  hung  on  high, 

Betwixt  the  nights  and  days  divides  the  sky, 
Then  yoke  your  oxen,  sow  your  winter  grain, 
Till  cold  December  comes  with  driving  rain." 

The  Greeks  declare  that  the  balance  was  placed  among  the  stars  to  perpetuate  the 
memory  of  Mochus,  the  inventor  of  weights  and  measures. 

Those  who  refer  the  constellations  of  the  Zodiac  to  the  twelve  tribes  of  Israel  ascribe 
the  Balance  to  Asher. 

TELESCOPIC  OBJECTS. 

1.  a  LIBRAE— A  wide  DOUBLE  STAR;  R.  A.  14h.  42m.  02s. ;  Dec.  S.  15°  22'  3".    A  8,  pal* 
yeilow;  B  6,  light  grey.    Carry  a  line  from  Arcturus  to  Spica;  and  from  thence  a  rect- 
angular one  about  22°  to  the  eastward. 

2.  ft  LIBR..E — A  loose  DOUBLE  STAR;  R.  A.  15h.  08m.  24s. ;  Dec.  S.  8°  47'  4".    A  2%,  pale 
emerald ;  B  12,  light  blue. 

3.  £  LIBRAE— A  fine  TRIPLE  STAR,  between  Libra  and  the  right  leg  of  Ophiuchus,  16°  from 
Antares,  towards  Serpentis ;    R.  A.  15h.  55m.  85s.;    Dec.  S.  10°  55' 6".     A  4 H,  bright 
white ;  B  5,  pale  yellow ;  C  7J<$,  grey.    Map  VIII.,  Fig.  11. 

4.  A  CLOSE  CLUSTER,  over  the  beam  of  the  Scales ;  R.  A.  15h.  10m.  26s. ;  Dec.  N.  2°  41'  S". 
A  superb  object,  with  a  bright  central  blaze,  and  outlines  in  all  directions.    Map  IX., 
Fig.  51.    Appears  nebulous  through  small  instruments. 

5.  A  LARGE  COMPRESSED  CLUSTER  of  minute  stars ;  R.  A.  15h.  08m.  06s. ;  Dec.  S.  20°  26'  7*. 
Faint  and  pale. 

HISTORY.— Who  was  Virgo,  Ac.?      Remark  of  Maurice ?    What  general  supposition? 
What  other  explanations? 
IY.LESCOPIC  OBJECTS.— Alpha ?    Beta?    What  triple  star ?    Map?    Clusters  and  Map ? 


ERPENS.  93 


SEEPED  (THE  SERPENT).— PLATE  Y. 

183.  There  are  no  less  than  four  kinds  of  serpents  placed 
among  the  constellations.     The  first  is  the  Hydra,  which  is  situ- 
ated south  of  the  Zodiac,  below  Cancer,  Leo  and  Virgo ;   the 
«econd  is  Hydrus,  which  is  situated  near  the  south  pole;   the 
third  is  Draco,  which  is  situated  about  the  north  pole  ;  and  the 
fourth  is  the  serpent  called  Serpens   Ophiuchi,  and  is  situated 
chiefly  between  Libra  and  Corona  Borealis.     A  large  part  of 
this  constellation,  however,  is  so  blended  with  Ophiuchus,  the 
Serpent-Bearer,  who  grasps  it  in  both  hands,  that  the  concluding 
description  of  it  will  be  deferred  until  we  coine  to  that  constel- 
lation. 

"  The  Serpens  Ophiuchi  winds  his  spire 
Immense :  fewer  by  ten  his  figure  trace ; 
One  of  the  second  rank ;  ten  shun  the  sight ; 
And  seven,  he  who  bears  the  monster  hides." 

184.  Those  stars  which  lie  scattered  along  for  about  25°,  in  a 
serpentine  direction  between  Libra  and  the  Crown,  mark  the 
body  and  head  of  the  Serpent. 

About  10°  directly  S.  of  the  Crown  there  are  three  stars  of 
the  3d  magnitude,  which,  with  several  smaller  ones,  distinguish 
the  head.  * 

185.  Unuk,  of  the  2d  magnitude,  is  the  principal  star  in  this 
constellation.     It  is  situated  in  the  heart,  about  10°  below  those 
in  the  head,  and  may  be  known  by  its  being  in  a  line  with,  and 
between,  two  stars  of  the  3d  magnitude — the  lower  one,  marked 
Epsilon,  being  2^-°,  and  the  upper  one,  marked  Delta,  about  5^-° 
from  it.     The  direction  of  this  line  is  N.  N.  W.  and  S.  S.  E 
Unuk  may  otherwise  be  known  by  means  of  a  small  star,  just 
above  it,  marked  Lambda. 

In  that  part  of  the  Serpent  which  lies  between  Corona  Borealis  and  the  Scales,  about 
a  dozen  stars  may  be  counted,  of  which  five  or  six  are  conspicuous. 
For  the  remainder  of  this  constellation,  the  student  is  referred  to  Serpentarius. 

"Vast  as  the  starry  Serpent,  that  on  high 
Tracks  the  clear  ether,  and  divides  the  sky, 
And  southward  winding  from  the  Northern  Wain. 
Shoots  to  remoter  spheres  its  glittering  train."— Statins. 

HISTORY. 

The  Hivites,  of  the  Old  Testament,  were  worshipers  of  the  Serpent,  and  were  called 
Ophites.  The  idolatry  of  these  Ophites  was  extremely  ancient,  and  was  connected  with 

183.  How  many  serpents  among  the  constellations?  Describe  each.  Which  here 
referred  to?  Is  it  fully  described ?  184.  What  stars  mark  the  body  and  head?  185. 
Name  the  principal  star.  Where  situated  and  how  known  ? 

HISTORY  —What  said  of  the  Hivites?  Tradition  respecting  Ophiuchus?  Supposed 
S.ripture  reference? 


94  ASTRONOMY. 

Siibfism-^  or  the  worship  of  the  host  of  heaven.  The  heresy  of  the  Ophites,  mentioned 
by  Mosheim,  in  his  Ecclesiastical  H 'story,  originated,  perhaps,  in  the  admission  into  the 
Christian  church  of  some  remnant  of  the  ancient  and  popular  sect  of  Sabeists,  who 
adored  the  celestial  Serpent. 

According  to  ancient  tradition,  Ophiuchus  is  the  celebrated  physician  2Esculapius,  son 
of  Apollo,  who  was  instructed  in  the  healing  art  by  Chiron  the  Centaur;  and  the  ser- 
pent, which  is  here  placed  in  his  hands,  is  understood  by  some  to  be  an  emblem  of  his 
sagacity  and  prudence;  while  othtis  suppose  it  was  designed  to  denote  his  skill  in  heal- 
ing the  bite  of  this  reptile.  Biblical  critics  imagine  that  this  constellation  is  alluded  to 
in  the  following  passage  of  the  book  of  Job  : — 

"  By  his  spirit  lie  hath  garnished  the  Heavens  ;  his  hand  hath  formed  the  crooked  ser- 
pent." Mr.  Green  supposes,  however,  that  the  inspired  writer  here  refers  to  Draco 
because  it  is  a  more  obvious  constellation,  being  nearer  the  pole  where  the  constellation, 
were  more  universally  noticed  ;  and  moreover,  because  it  is  a  more  ancient  constellation 
than  the  Serpent,  and  the  hieroglyphic  by  which  the  Egyptians  usually  represented  the 
heavens. 

TELESCOPIC  OBJECTS. 

1.  a  SERPEXTIS  (  UntiK) — A  star  with  a  minute  companion  on  the  heart  of  the  Serpent ; 
R.  A.  I5h.  36m.  23s. ;  Dec.  N.  6"  55'  9".    A  2^,  pale  yellow ;  B  15,  fine  blue.    An  extremely 
delicate  object. 

2.  tf  SKKPENTTS — A  delicate  DOUBLE  STAR  in  the  Serpent's  under  jaw;  R.  A.  15h.  38m. 
4Ss. ;  Dec.  N.  15"  55'  7'.     A  3^,  and  B  10,  both  pale  blue. 

3.  (5  SKRPKNTIS — An  elegant  DOUBLE  STAR  in  the  bend  of  the  neck  ;  R.  A.  15h.  27m.  10s. ; 
Dec.  N.  11°  04'  7".    A  3,  bright  white  ;  B  5,  bluish  white.    A  fine  object,  about  5°  N.  W. 
of  Unak. 

4.  r]  SBRPENTIS — A  star  with  a  minute  companion  in  the  Serpent's  body,  nearly  midway 
between  r/  Ophiuchi  and  C-Aquilae;  R.  A.  18h.  13m.  02s.;  Dec.  S.  2°  56'  0".     A  4,  golden 
yellow;  B  13,  pale  lilac.     A  delicate  and  difficult  object. 

5.  v  SKRPENTIS — A  wide  DOUBLE  STAR  in  the  middle  of  the  Serpent,  4°  northeast  of  rj  \ 
R.  A.  17h.  llm.  49s.;  Dec.  S.  12°  40'  7"'    A  4)$,  pale  sea-green;  B  9,  lilac,  with  a  third 
star  in  the  field. 

6.  A  delicate  DOUBLE  STAR;  R.  A.  15h.  llm.  08s.;  Dec.  N.  2"  22'  6'.    A  5^,pale  yellow 
B  10}$,  light  grey.     Look  9°  southwest  of  a  Serpentis,  24°  southeast  of  Arcturus. 


CORONA  BOREALIS  (THE  NORTHERN  OKOWN).— MAP  V. 

186.  This  beautiful   constellation   may  be  easily  known   by 
means  of  its  six  principal  stars,  which  are  so  placed  as  to  form 
a  circular  figure,  very  much  resembling  a  wreath  or  crown.     It 
is  situated  directly  north  of  the  Serpent's  head,  between  Bootes 
on  the  west,  and  Hercules  on  the  east. 

This  asterism  was  known  to  the  Hebrews  by  the  name  of  Ataroth,  and  by  this  namo 
the  stars  in  Corona  Borealis  are  called,  in  the  East,  to  this  day. 

187.  Alphacca,  of  the  2d  magnitude,  is   the   brightest    and 
middle  star  in  the  diadem,  and  about  11°  E.  of  Mirac,  in  Bootes. 
It  is  very  readily  distinguished  from  the  others  both  on  account 
of  its  position  and  superior  brilliancy.     Alphacca,  Arcturus,  and 
Seginus,  form  nearly  an  isosceles  triangle,  the  vertex  of  which  is 
at  Arcturus. 

TELESCOPIC  OBJECTS.— Alpha?    Beta?    Delta?    Eta?    Nu?    &c. 

186.  How  may   Corona  Borealis  be  known?    Where  situated?    Its  Hebrew  namt-i 
187.  Describe  Aiphacca?    How  distinguished  ?    What  triangle  ? 


CORONA    BOREALIS.  95 

188.  This  constellation  contains  twenty-one  stars,  of  which 
only  six  or  eight  are  conspicuous ;  and  most  of  those  are  not 
larger  than  the  3d  magnitude.  Its  mean  declination  is  30° 
north,  and  its  mean  right  ascension  235°;  its  center  is  therefore 
on  the  meridian  about  the  last  of  June,  and  the  first  of  J  uly. 

"And,  near  to  llelice,  effulgent  rays 
Beam,  Ariadne,  from  thy  starry  crown: 
Twenty  and  one  her  stars ;  but  eight  alone 
Conspicuous ;  one  doubtful,  or  to  claim 
The  second  order,  or  accept  the  third." 

HISTORY. 

This  beautiful  little  cluster  of  stars  is  said  to  be  in  commemoration  of  a  crown  pre- 
sented by  Bacchus  to  Ariadne,  the  daughter  of  Minos,  second  king  of  Crete.  Theseus, 
king  of  Athens  (1235  B.  C.),  was  shut  up  in  the  celebrated  labyrinth  of  Crete,  to  be 
devoured  by  the  ferocious  Minotaur  which  was  confined  in  that  place,  and  which  usually 
fed  upon  the  chosen  young  men  and  maidens  exacted  from  the  Athenians  as  a  yearly 
tribute  to  the  tyranny  of  Minos;  but  Theseus  slew  the  monster,  and  being  furnished  with 
a  clew  of  thread  by  Ariadne,  who  was  passionately  enamored  of  him,  he  extricated 
himself  from  the  difficult  windings  of  his  confinement. 

He  afterward  married  the  beautiful  Ariadne  according  to  promise,  and  carried  her 
away ;  but  when  he  arrived  at  the  island  of  Naxos,  he  deserted  her,  notwithstanding  he 
had  received  from  her  the  most  honorable  evidence  of  attachment  and  endearing  tender- 
ness. Ariadne  was  so  disconsolate  upon  being  abandoned  by  Thesvus,  that,  as  some  say, 
she  hanged  herself;  but  Plutarch  say*  that  she  lived  many  years  after,  and  was  espoused 
to  Bacchus,  who  loved  her  with  much  tenderness,  and  gave  her  a  crown  of  seven  stars 
which,  after  her  death,  was  placed  among  the  stars. 

"  Resolves,  for  this  the  dear  engaging  dame 

Should  shine  forever  in  the  foils  of  fame; 

And  bids  her  crown  among  the  stars  be  placed, 

And  with  an  eternal  constellation  graced. 

The  golden  circlet  mounts;  and,  as  it  flies, 

Its  diamonds  twinkle  in  the  distant  skies; 

There,  in  their  pristine  form,  the  gemray  rays 

Between  Alcides  and  the  Dragon  blaze." 

Manilius,  in  the  first  book  of  his  Astronomicon,  thus  speaks  of  the  Crown. 
"Near  to  Bootes  the  bright  crown  is  view'd, 

\nd  shines  with  stars  of  different  magnitude: 

Or  placed  in  front  above  the  rest  displays 

A  vigorous  light,  and  darts  surprising  rays. 

This  shone,  since  Theseus  first  his  faith  betray'd, 

The  monument  of  the  forsaken  maid." 

\ 

TELESCOPIC  OBJECTS. 

.  a  CORONA  BOREALIS  (Alphaccd) — A  bright  star  with  a  distant  companion;  R.  A. 
15h.  27m.  54s.;  Dec.  N.  27°  15'  2".  A  2,  brilliant  white;  B  8,  pale  violet. 

2.  y  CORONA  BOREALIS — A  most  difficult  BINARY  STAR,  2)3°  from  Alphacca;  R.  A.  15h. 
80m.  Ols. ;  Dec.  N.  26°  48'  4";  with  a  distant  companion.  A  6,  flushed  white;  B,  uncer- 
tain ,  C  10,  pale  lilac. 

8.  s  COROX.*  BOREALIS — A  fine  DOUBLE  STAR,  10*  north  and  a  Httle  easterly  frooi  Alphacca ; 
R.  A  15h.  33m.  21s. ;  Dec.  N.  87"  09'  6".  A  5,  bluish  white ;  B  6,  smalt  blue  A  beauti- 
ful object. 

4.  if  COROS*  BOREALIS — A  BINARY  STAR,  midway  between  the  Northern  Crown  and  the 
club  of  Bootes ;  R.  A.  15h.  16m.  36s. ;  Dec.  N.  80'  52'  2".  A  north-northwest  ray  from  a 
C., rouse,  through  J,  and  half  as  far  again,  will  hit  it.  A  6,  white ;  B  65$,  golden  yellow. 


1S8.  How  many  stars  in  this  constellation?    Their  magnitudes?    Mean  declination 
and  right  ascension  ? 

HISTORY. — Story  respecting  Theseus  and  Arindne? 
TELESCOPIC  OBJECTS. — Alpha?    Oamina?    Zeta?    Eta? 


96  ASTRONOMY. 

Sir  John  Herschel  considered  this  the  most  remarkable  binary  star  known,  and  the  on'y 
one  that  had  completed  a  whole  revolution  since  its  discovery.  Estimated  period  432 
vears. 


URSA  MINOR  (THE  LESSEE  BEAE).— MAP  VI. 

189.  This  constellation,  though  not  remarkable  in  its  appear 
ance,  and  containing  but  few  conspicuous  stars,  is,  nevertheless, 
justly  distinguished  from  all  others  for  the  peculiar  advantage 
which  its  position  in  the  heavens  is  well  known  to  afford  to  nau- 
tical astronomy,  and  especially  to  navigation  and  surveying. 

The  stars  in  this  group  being  situated  near  the  celestial  pole, 
appear  to  revolve  about  it,  very  slowly,  and  in  circles  so  small 
as  never  to  descend  below  the  horizon.  Hence  Ursa  Minor  will 
be  above  or  below,  to  the  right  or  left  of  the  pole  star,  accord- 
ing to  the  hour ;  as  he  makes  the  entire  circuit  from  east  to  west 
every  24  hours. 

190.  In  all  ages  of  the  world,  this  constellation  has  been  more 
universally  observed,  and  more  carefully  noticed  than  any  other, 
on  account  of  the  importance  which  mankind  early  attached  to 
the  position  of  its  principal  star.     This  star,  which  is  so  near  the 
true  pole  of  the  heavens,  ha*  from  time  immemorial  been  deno- 
minated the  NORTH  POLAR  STAR.     By  the  Greeks  it  is  called 
Cynosyrt ;   by  the  Romans,   Cynosura,  and  by  other  nations, 
Alruccalah.     In  most  modern  treatises  it  bears  the  name  of  Po- 
laris, or  Alpha  Polaris. 

191  Polaris  is  of  the  3d  magnitude,  or  between  the  2d  and 
3d,  and  situated  a  little  more  than  a  degree  and  a  half  from  the 
true  pole  of  the  heavens,  on  that  side  of  it  which  is  toward  Cas- 
siopeia and  opposite  to  Ursa  Major.  Its  position  is  pointed  out 
by  the  direction  of  the  two  Pointers,  Merak  and  Dubhe,  which 
lie  in  the  square  of  Ursa  Major.  A  line  joining  Beta  Cassio- 
peiae,  which  lies  at  the  distance  of  32°  on  one  side,  and  Megrez, 
which  lies  at  the  same  distance  on  the  other,  will  pass  through 
the  polar  star. 

Of  the  Pole  Star  Capt.  Smyth  observes :  At  present  it  is  only  1°  33'  from  the  polar  point, 
•ind  by  its  northerly  precession  in  declination  will  gradually  approach  to  within  26'  30* 
:>f  it.  This  proximity  to  the  actual  pole  will  occur  in  A.  D.  2095,  but  will  not  recur  for 
12,860  years.  The  period  of  the  revolution  of  the  celestial  equinoctial  pole  about  the 
pole  of  the  ecliptic,  is  nearly  26,000  years ;  the  north  celestial  pole,  therefore,  will  be 
vbout  13,000  years  ;  hence,  nearly  49°  from  the  present  polar  star. 

189.  For  what  is  Ursa  Minor  distinguished  ?  What  said  of  its  situation  and  change  of 
position?  190.  What  said  of  the  notice  taken  of  it?  Position  of  its  principal  star f 
[ts  Greek  and  Latin  names,  &c.  ?  191.  Describe  Polaris?  How  found?  lieoiar'is  of 
Capt.  Smyth  respecting? 


URSA    MINOR  97 

192.  So  general  is  the  popular  notion,  that  the  North  Polar 
Star  is  the  true  pole  of  the  world,  that  even  surveyors  and  navi- 
gators, who  have  acquired  considerable  dexterity  in  the  use  oi 
the  compass  and  the  quadrant,  are  not  aware  that  it  ever  had 
any  deviation,  and  consequently  never  make  allowance  for  any. 
All  calculations  derived  from  the  observed  position  of  this  star, 
which  are  founded  upon  the  idea  that  its  bearing  is  always  due 
north  of  any  place,  are  necessarily  erroneous,  since  it  is  in  this 
position  only  twice  in  twenty-four  hours  ;  once  when  above,  and 
once  when  below  the  pole. 

193.  Hence,  it  is  evident  that  the  surveyor  who  regulates  his 
uompass  by  the  North  Polar  Star,  must  take  his  observation 
when  the  star  is  on  the  meridian,  either  above  or  below  the  pole, 
or  make  allowance  for  its  altered  position  in  every  other  situa- 
tion.    For  the  same  reason  must  the  navigator,  who  applies  his 
Quadrant  to  this  star  for  the  purpose  of  determining  the  latitude 
he  is  in,  make  a  similar  allowance,  according  as  its  altitude  is 
greater  or  less  than  the  true  pole  of  the  heavens  ;  for  we  have 
seen  that  it  is  alternately  half  the  time  above  and  half  the  time 
Idow  the  pole. 

194.  The  method  of  finding  the^  latitude  of  a  place  from  the 
altitude  of  the  polar  star,  as  it  is  very  simple,  is  very  often 
resorted  to.     Indeed,  in  northern  latitudes,  the  situation  of  this 
star  is  more  favorable  for  this  purpose  than  that  of  any  other  of 
the  heavenly  bodies,  because  a  single  observation,  taken  at  any 
hour  of  the  night  with  a  good  instrument,  will  give  the  true  lati- 
tude, without  any  calculation  or  correction,  except  that  of  its 
polar  aberration. 

If  the  polar  star  always  occupied  that  point  in  the  heavens  which  is  directly  opposite 
the  north  pole  of  the  earth,  it  would  be  easy  to  understand  how  latitude  could  be  deter- 
mined from  it  in  the  northern  hemisphere;  for  in  this  case,  to  a  person  on  the  equator, 
the  poles  of  the  world  would  be  seen  in  the  horizon.  Consequently,  the  star  would 
appear  just  visible  in  the  northern  horizon,  without  any  elevatiun.  Should  the  person 
now  travel  one  degree  toward  the  north,  he  would  see  one  degree  below  the  star,  and  ht, 
would  think  it  had  risen  one  degree. 

And  since  we  always  see  the  whole  of  the  upper  hemisphere  at  one  view,  when  there 
ii,  nothing  in  the  horizon  to  obstruct  our  vision,  it  follows  that  if  we  should  travel  10° 
north  of  the  equator,  we  should  see  just  10°  below  the  pole,  which  would  then  appear  to 
have  risen  10° ;  and  should  we  stop  in  the  42d  degree  of  north  latitude  we  should,  in  like 
manner,  have  our  horizon  just  42°  below  the  pole,  or  the  pole  would  appear  to  have  an 
elevation  of  42°.  Whence  we  derive  this  general  truth  :  The  devotion  of  the  pole  of  th& 
equator  is  always  equal  to  the  latitude  of  the  place  of  observation. 

Any  instrument,  then,  which  will  give  us  the  altitude  of  the  north  pole,  will  give  us 
also  the  latitude  of  the  place. 

The  method  of  illustrating  this  phenomenon,  is  given  in  most  treatises  on  the  globe, 

192.  What  popular  error  ?  193.  When  is  the  pole  star  a  safe  guide  for  the  surveyor 
or  mariner?  What  allowances  should  be  made  by  each?  194.  What  said  of  finding 
the  latitude  by  observations  upon  the  pole  star?  What  general  rule  stated?  Whu"' 
error  ommitted  ? 


#8  ASTRONOMY. 

and  as  adopted  by  teachers  generally,  la  to  tell  the  scholar  that  the  north  pole  ristj 
higher  and  higher,  as  he  travels  farther  and  farther  toward  it.  In  oth'%r  words,  what- 
ever number  of  degrees  he  advances  toward  the  north  pole,  so  many  degrees  will  it  rise 
above  his  horizon.  This  is  not  only  an  obvious  error  in  principle,  but  it  misleads  the 
apprehension  of  the  pupil.  It  is  not  that  the  pole  i*  el&v<ited,  but  that  our  horizon,  is 
dtpretsxed  as  we  advance  toward  the  north.  The  same  objection  lies  against  the  artifi- 
cial globe;  for  it  ought  to  be  so  fixe.l  that  the  horizon  might  be  raised  or  depressed,  and 
the  pole  remain  in  its  own  invariable  position. 

195.  Ursa  Minor  contains  twenty-four  stars,  including  three 
of  the  3d  magnitude  and  four  of  the  4th.     The  seven  principal 
stars  are  so  situated  as  to  form  a  figure  very  much  resembling 
that  in  the  Great   Bear,  only  that  the  Dipper  is  reversed,  and 
about  one  half  as  large  as  the  one  in  that  constellation. 

196.  The  first  star  in  the  handle,  called  Polaris,  is  the  polar 
star,  around  which  the  rest  constantly  revolve.     The  two  last  in 
the  bowl  of  the  Dipper,  corresponding  to  the  Pointers  in  the 
Great   Bear,  are  of  the  3d  magnitude,  and  situated  about  15° 
from  the  pole.     The  brightest  of  them  is  called  Kochab,  which 
signifies  an  axle  or  hinge,  probably  in  reference  to  its  moving  so 
near  the  axis  of  the  earth. 

Koclmb  may  be  easily  known  by  its  being  the  brightest  and  middle  one  of  the  three 
conspicuous  stars  forming  a  row,  one  of  which  is  about  2%  and  the  other  3°  from  Kochab. 
The  two  brighest  of  these  are  situated  in  the  breast  and  shoulder  of  the  animal,  about 
8"  apart,  and  are  called  the  Giuirdu  or  Pointers  of  Ursa  Minor.  They  are  on  the  meri- 
dian about  the  20th  of  June,  but  may  be  seen  at  all  hours  of  the  night,  when  the  sky  is 
clear. 

197.  Of  the  four  stars  which  form  the  bowl  of  the  Dipper, 
one  is  so  small  as  hardly  to  be  seen.     They  lie  in  a  direction 
toward  Gamma,  in  Cepheus  ;  but  as  they  are  continually  chang- 
ing their  position  in  the  heavens,  they  may  be  much  better  traced 
out  from  the  map,  than  from  description. 

Kochab  is  about  25°  distant  from  Benetnasch,  and  about  24° 
from  Dubhe,  and  hence  forms  with  them  a  very  nearly  equi- 
lateral triangle. 

"  The  Lesser  Bear 

Leads  from  the  pole  the  lucid  band  :  the  stars 
\Vhich  form  this  constellation,  faintly  shine, 
Twice  twelve  in  number;  only  one  beams  forth 
Conspicuous  in  high  splendor,  named  by  Greece 
The  Cynosure;  by  us,  the  I'OLAB  rfTAK." 

HISTORY. 

The  prevailing  opinion  is  that  Ursa  Major  and  Ursa  Minor  are  the  nymph  Calisto  aiivl 
her  son  Areas,  *nd  that  they  were  transformed  into  bears  by  the  enraged  and  imperious 
Juno,  and  afterward  translated  to  heaven  by  the  favor  of  Jupiter,  lest  they  might  be 
destroyed  by  the  huntsmen. 

The  Chinese  claim  that  the  emperor  Hong-ti,  the  grandson  of  Noah,  hrst  discovered 


195.  Number  o*  stars  in  Ursa  Minor?  Their  magnitudes?  How  situated  ?  196.  De- 
Bcnne  Solaris.  Kochab,  and  the  Guards  or  Pointers?  197.  Are  all  the  stars  distinctly 
Visible?  Direction?  What  triangle  ? 

HISTORY. — What  prevailing  opinion,  or  myth?     Chinese  claim  ?     Phemcians?     Greets 


URSA    MINOR.  9U 

the  polar  star,  and  applied  it  to  purposes  of  navigation.  It  is  certain  that  it  was  used 
for  this  purpose  in  a  very  remote  period  of  antiquity.  From  various  passages  in  tb.8 
ancients,  it  is  manifest  that  the  Phenicians  steered  by  Cynosura,  or  the  Lessor  Bear; 
vhereas,  the  mariners  of  Greece,  and  some  other  nations,  steered  by  the  Greater  Bear, 
called  Helice,  or  Helix. 

Lucan,  a  Latin  poet,  who  flourished  about  the  time  of  the  birth  of  our  Saviour,  thiw 
adverts  to  the  practice  of  steering  vessels  by  Cynosura  : — 

"  Unstable  Tyre  now  knit  to  firmer  ground, 
With  Sidon  for  her  purple  shells  renown'd, 
Safe  in  the  Cynosure  their  glittering  guide 
With  well-directed  navies  stem  the  tide." 

ROWE'S  Translation,  B.  iii. 

The  following  extracts  from  other  poets  contain  allusions  to  the  same  fact: 

"  Phenicia,  spurning  Asia's  bounding  strand, 
By  the  bright  Pole  star's  steady  radiance  led, 
Bade  to  the  winds  her  daring  sails  expand, 
And  fearless  plough'd  old  Ocean's  stormy  bed." 

MAURICE'S  Elegy  on  Sir  W.  Jones, 

"  Ye  radiant  signs,  who,  from  the  ethereal  plain 
Sidonians guide,  and  Greeks  upon  the  main, 
Who  from  your  poles  all  earthly  things  explore, 
And  never  set  beneath  the  western  shore." 
OVID'S  Triatia. 

"  Of  all  yon  multitude  of  golden  stars, 
Which  the  wide  rounding  sphere  incessant  bears. 
The  cautious  mariner  relies  on  none, 
But  keeps  him  to  the  constant  pole  alone." 

LUCAN'S  Pharsalia,  B.  viii.  v.  225. 

Ursa  Major  and  Ursa  Minor  are  sometimes  called  Triones,  and  sometimes  the  Greater 
nnd  Lesser  Wains.  In  Pennington's  Memoirs  of  the  learned  Mrs.  Carter,  we  have  the 
following  beautiful  lines  :— 

44  Here  Cassiopeia  fills-a  lucid  throne, 
There,  blaze  the  splendors  of  the  Northern  Crown  ; 
While  the  slow  Car,  the  cold  Triones  roll 
O'er  the  pale  countries  of  the  frozen  pole  : 
Whose  faithful  beams  conduct  the  wandering  ship 
Through  the  wide  desert  of  the  pathless  deep." 

Thales,  an  eminent  geometrician  and  astronomer,  and  one  of  the  seven  wise  men  of 
Greece,  who  flourished  six  hundred  years  before  the  Christian  era,  is  generally  reputed 
to  be  the  inventor  of  this  constellation,  and  to  have  taught  the  use  of  it  to  the  Phenician 
navigators  ;  it  is  certain  that  he  brought  the  knowledge  of  it  with  him  from  Phenice  into 
Greece,  with  many  other  discoveries  both  in  astronomy  and  mathematics. 

Until  the  properties  of  the  magnet  were  known  and  applied  to  the  use  of  navigation, 
and  for  a  long  time  after,  the  north  polar  star  was  the  only  sure  guide.  At  what  time  the 
attractive  powers  of  the  magnet  were  first  known,  is  not  certain  ;  they  were  known  in 
Europe  about  six  hundred  years  before  the  Christian  era ;  and  by  the  Chinese  records,  ft 
is  said  that  its  polar  attraction  was  known  in  that  country  at  least  one  thousand  years 
earlier. 

TELESCOPIC  OBJECTS. 

1.  a  URSJS  MINORIS  (Polaris)— A  DOUBLE  STAR;  R.  A.  Ih.  2m.  10s.;  Dec.  N.  88*  27'  4*. 
A  2)$,  topaz  yellow ;  B  9%,  pale  white:    Map  VIII.,  Fig.  1'J. 

2.  (3  URS.S  MINORIS  (ITochab) — A  star  with  a  distant  companion  4n  the  left  shoulder; 
R.  A.  14h.  51m.  14s. ;  Dec.  N.  74°  48'  2'.    A  3,  reddish ;  B  11,  pale  grey— several  small 
jtars  in  the  field 

3.  d  URS^E  MIKORIS— A  star  with  a  very  distant  telescopic  companion  in  the  middle  of 
(he  tail  of  the  figure ;  R.  A.  18h.  23m.  56s. ;  Dec.  N.  86°  35'  4".    A  8,  greenish   tinge ; 
B  12,  grey. 

What  proofs  from  the  poets?  What  other  names  for  Ursa  Major  and  Ursa  Minor?  Wlm* 
mid  of  Thales?  Use  of  the  pole  star?  The  magnet? 

OBJBCTS.— Alpha?    Show  on  li.e  map,  Beta— Delta— Epsil on— Zeta. 

5 


(00  ASTRONOMY. 

4.  e  URS^B  MAORIS — A  star  with  a  minute  companion,  at  the  root  of  the  tail ;  R.  A- 
17h.  02m.  37s. ;  Dec.  N.  82°  17'  01'.    A  4,  bright   yellow;  B  12,  pale  blue;  three  other 
telescopic  stars  in  the  field.    It  is  easily  found,  being  the  third  star  from  Polaris 

5.  £  URS*  MINORIS — A  DOUBLE  STAR  in  the  middle  of  the  body ;  R.  A.  15h.  4'Jm.  52s.  5 
Dec.  N.  78°  16'  07'.    A  4,  flushed  white ;  B  11,  bluish  •  with  a  yellow  star  of  the  9th  majj- 
aitudc  in  the  field. 


CHAPTER  IX. 

CONSTELLATIONS    ON   THE   MERIDIAN    IN   JULY. 

SCORPIO  (THE  SCOEPION).— MAP  Y. 

198.  THIS  is  the  eighth  sign,  and  ninth  constellation,  in  the 
order  of  the  Zodiac.     It  presents  one  of  .the  most  interesting 
groups  of  stars  for  the  pupil  to  trace  out  that  is  to  be  found  in 
the  southern  hemisphere.     It  is  situated  southward  and  east 
ward  of  Libra,  and  is  on  the  meridian  the  10th  of  July. 

The  sun  enters  this  sign  on  the  23d  of  October,  but  does  not  reach  the  constellation 
before  the  20th  of  November.  When  astronomy  was  first  cultivated  in  the  East,  the  two 
solstices  and  the  two  equinoxes  took  place  when  the  sun  was  in  Aquarius  and  Leo,  Tau- 
rus and  Scorpio,  respectively. 

199.  Scorpio  contains,  according  to  Flamsted,  forty-four  stars, 
including -one  of  the  1st  magnitude,  one  of  the  2d,  and  eleven  of 
the  3d.     It  is  readily  distinguished  from  all  others  by  the  pecu- 
liar luster  and  the  position  of  its  principal  stars. 

Antares  is  the  principal  star,  and  is  situated  in  the  heart  of 
the  Scorpion,  about  19°  east  of  Zubenelgubi,  the  southernmost 
star  in  the  Balance.  Antares  is  the  most  brilliant  star  in  that 
region  of  the  skies,  and  may  be  otherwise  distinguished  by  its 
remarkably  red  appearance.  Its  declination  is  about  26°  S 
It  comes  to  the  meridian  about  three  hours  after  Spica  Virginis, 
or  fifty  minutes  after  Corona  Borealis,  on  the  10th  of  July.  It 
is  one  of  the  stars  from  which  the  moon's  distance  is  reckoned 
for  computing  the  longitude  at  sea. 

There  are  four  great  stars  in  the  heavens,  Fomalhaut,  Aldebaran,  Regulus,  and 
Antares,  which  formerly  answered  to  the  solstitial  and  equinoctial  points,  and  which 
/cere  much  noticed  by  the  astronomers  of  the  East. 

200.  About  sy  northwest  of  Antares,  is  a  star  of  the  2d 

198.  Order  of  Scorpio  among  the  signs,  Ac.?  Its  comparative  interest?  Situation? 
When  does  the  sun  enter  this  sign  ?  When  the  constellation  f  How  with  the  solstices 
<vnd  equinoxes  anciently?  Why  not  so  now?  199.  Number  and  magnitudes  of  the 
cturs  in  Scorpio?  How  distinguished ?  Name  and  position  of  its  principal  star?  Hoy 
Unown  ?  What  use  made  of  it  ?  What  three  other  stars  mentioned ?  200.  What  other 


SCORPIO.  101 

magnitude,  in  the  head  of  the  Scorpion,  called  Graffias.  It  is 
but  one  degree  north  of  the  earth's  orbit.  It  may  be  recognized 
by  means  of  a  small  star,  situated  about  a  degree  northeast  of 
it,  and  also  by  its  forming  a  slight  curve  with  two  other  stars 
of  the  3d  magnitude,  situated  below  it,  each  about  3°  apart. 
The  broad  part  of  the  constellation  near  Graffias,  is  powdered 
with  numerous  small  stars,  converging  down  to  a  point  at 
Antares,  and  resembling  in  figure  a  boy's  kite. 

201.  As  you  proceed  from  Antares,  there  are  ten  conspicuous 
stars,  chiefly  of  the  3d  magnitude,  which  mark  the  tail  of  the 
kite,  extending  down,   first  in  a  south-southeasterly  direction 
about  17°,  thence  easterly  about  8°  further,  when  they  turn, 
and  advance  about  8°  toward  the  north,  forming  a  curve  like  a 
shepherd's  crook,   or  the  bottom  part  of  the  letter  S.     This 
crooked  line  of  stars,  forming  the  tail  of  the  Scorpion,  is  very 
conspicuous,  and  may  be  easily  traced. 

The  first  star  below  Antares,  which  is  the  last  in  the  back,  is  of  only  the  4th  magni- 
tude. It  is  about  2°  southeast  of  Antares,  and  is  denoted  by  the  Greek  name  of  T. 

Epsilon,  of  the  3d  magnitude,  is  the  second  star  from  Antares,  and  the  first  in  the 
tail  It  is  situated  about  7°  below  the  star  T,  but  inclining  a  little  to  the  east. 

Jfu,  of  the  3d  magnitude,  is  the  3d  star  from  Antares.  It  is  situated  4%°  below  Epsi- 
lon.  It  may  otherwise  be  known  by  means  of  a  small  star  close  by  it,  on  the  left. 

Zeta,  of  about  the  same  magnitude,  and  situated  about  as  far  below  Mu,  is  the  fourth 
star  from  Antares.  Here  the  line  turns  suddenly  to  the  east. 

Eta,  also  of  the  3d  magnitude,  is  the  fifth  star  from  Antares,  and  about  3J$°  east  of 
Zeta. 

Theta,  of  the  same  magnitude,  is  the  sixth  star  from  Antares,  and  about  4^'  east 
of  Eta.  Here,  the  line  turns  again,  curving  to  the  north,  and  terminates  in  a  couple 
of  stars. 

Iota  is  the  seventh  star  from  Antares,  3 %*  above  Theta,  curving  a  little  to  the  left. 
It  is  a  star  of  the  3d  magnitude,  and  may  be  known  by  means  of  a  small  star,  almost 
touching  it,  on  the  east. 

Kappa,  a  star  of  equal  brightness,  is  less  than  2"  above  Iota,  and  a  little  to  the  right. 

LesittJi,  of  the  3d  magnitude,  is  the  brightest  of  the  two  last,  in  the  tail,  and  is  situated 
about  3°  above  Kappa,  still  further  to  the  right.  It  may  readily  be  known  by  means  of 
a  smaller  star,  close  by  it,  on  the  west. 

202.  This  is  a  very  beautiful  group  of  stars,  and  easily  traced 
out  in  the  heavens.     It  furnishes  striking  evidence  of  the  facility 
with  which   most  of  the   constellations  may  be  so  accurately 
delineated,  as  to  preclude  everything  like   uncertainty  in  the 
knowledge  of  their  relative  situation, 

"  The  heart  with  luster  of  amazing  force, 
Refulgent  vibrates ;  faint  the  other  parts, 
And  ill-defined  by  stars  of  meaner  note." 

HISTORY. 

This  sign  was  anciently  represented  by  various  symbols,  sometimes  by  a  snake,  and 
bometimes  by  a  crocodile ;  but  most  commonly  by  the  scorpion.  This  last  symbol  is 


Rtar  described  ?    Size  and  position?    How  recognized?    What  said  of  the  broad  part  or 
body  of  Scorpio?        201.  What  stars  form  the  tail  of  Scorpio?    Are  they  conspicuouo  ? 
Name  and  describe  in  detail?         202.  General  remarks  respecting  this  constellation? 
JlrSTOUY.— How  was  Scorpio  anciently  delineated?     How  regarded  by  ancient  astro'.o 


102  ASTRONOMY. 

found  on  the  Mithraic  monuments,  which  is  pretty  good  evidence  that  these  monuments 
yere  constructed  when  the  vernal  equinox  accorded  with  Taurus. 

On  f)oth  the  zodiacs  of  Dendera,  there  are  rude  delineations  of  this  animal ;  that  on 
the  portico  differs  considerably  from  that  on  the  other  zodiac,  now  in  the  Louvre. 

Scorpio  was  considered  by  the  ancient  astrologers  as  a  sign  accursed.  The  Egyptians 
Qxed  the  entrance  of  the  sun  into  Scorpio  as  the  commencement  of  the  reign  of  Typhon, 
when  the  Greeks  fabled  the  death  of  Orion.  When  the  sun  was  in  Scorpio,  in  the  month 
of  Atkyr,  as  Plutarch  informs  us,  the  Egyptians  inclosed  the  body  of  their  god  Osiris  in 
an  ark,  or  chest,  and  during  this  ceremony  a  grt-at  annual  festival  was  celebrated. 
Three  days  after  the  priests  had  inclosed  Osiris  in  the  ark,  they  pretended  to  have  found 
him  again.  The  death  of  Osiris,  then,  was  lamented  when  the  sun  in  Scorpio  descended 
to  the  lower  hemisphere,  and  when  he  arose  at  the  vernal  equinox,  then  Osiris  was  said 
to  be  born  anew. 

The  Egyptians  or  Chaldeans,  who  first  arranged  the  Zodiac,  might  have  placed  Scorpio 
in  this  part  of  the  heavens  to  denote  that  when  the  sun  enters  this  sign,  the  diseases 
Incident  to  the  fruit  season  would  prevail ;  since  Autumn,  which  abounded  in  fruit,  often 
brought  with  it  a  great  variety  of  diseases,  and  might  be  thus  fitly  represented  by  that 
venomous  animal,  the  scorpion,  who,  as  he  recedes,  wounds  with  a  sting  in  his  tail. 

Mars  was  the  tutelary  deity  of  the  Scorpion,  and  to  this  circumstance  is  owing  all  that 
largon  of  the  astrologers,  who  say  that  there  is  a  great  analogy  between  the  malign 
influence  of  the  planet  M>rs  and  this  sign.  To  this  also  is  owing  the  doctrine  of  the 
alchemists,  that  iron,  which  metal  they  call  Mars,  is  under  the  dominion  of  Scorpio  ;  so 
ibat  the  transmutation  of  it  into  gold  can  be  effected  only  when  the  sun  is  in  this  sign. 

The  constellation  of  the  Scorpion  is  very  ancient.  Ovid  thus  mentions  it  in  his  beau- 
tiful fable  of  Phaeton  :— 

"  There  is  a  place  above,  where  Scorpio  bent, 
In  tail  and  arms  surrounds  a  vast  extent ; 
In  a  wide  circuit  of  the  heavens  he  shines, 
And  fills  the  place  of  two  celestial  signs." 

According  to  Ovid,  this  is  the  famous  scorpion  which  sprang  out  of  the  earth  at  the 
command  of  Juno,  and  stung  Orion ;  of  which  wound  he  died.  It  was  in  this  way  the 
imperious  goddess  chose  to  punish  the  vanity  of  the  hero  and  the  hunter,  for  boasting 
that  there  was  not  on  earth  any  animal  which  he  could  not  conquer. 

"  Words  that  provoked  the  gods  once  from  him  fell, 
'No  beasts  so  fierce,'  said  he,  'but  I  can  quell;' 
When  lo  !  the  earth  a  baleful  scorpion  sent, 
To  kill  Latona  was  the  dire  intent ; 
Orion  saved  her,  though  himself  was  slain, 
But  did  for  that  a  spacious  place  obtain 
In  heaven  :  '  to  tiiee  my  life,'  said  she, '  was  dear, 
And/or  thy  merit  shine  illustrious  tliere" 

Although  both  Orion  and  Scorpio  were  honored  by  the  celestials  with  a  place  amonp 
the  stars,  yet  their  situations  were  so  ordered  that  when  one  rose  the  other  should  set, 
and  viee  versa;  so  that  they  never  appear  in  the  same  hemisphere  at  the  same  time. 

In  the  Hebrew  zodiac  this  sign  is  allotted  to  Dan,  because  it  is  written,  "  Dan  shall  be 
a  serpent  by  the  way,  an  adder  in  the  path." 

TELESCOPIC  OBJECTS. 

1-  n  SCORFII  (Antares) — A  bright  star  with  a  companion  in  the  heart  of  Scorpio ;  R.  A 
16h.  19m.  36s. ;  Dec.  S.  26°  04'  8".  A  1,  fiery  red  ;  B  8,  pale.  Very  dose. 

2.  0  SCORPII (Grajfias)— A  star  with  a  companion  in  the  head;  R.  A.  15h.  56m.  08s.* 
Dec.  S.  19°  21'  7".  A  2,  pale  white ;  B  5 J$,  lilac  tinge. 

8.  v  SCOBPII— A  neat  DOUBLE  STAR,  east  by  north  from  0  about  2" ;  R.  A.  ioh.  02m.  42s.  • 
Oec.  S.  19°  02'  8*.  A  4,  bright  white ;  B  7,  pale  lilac.  Professor  Mitchell  registers  this 
AS  a  triple  star. 

4.  a  SCORPII— A  delicate  DOUBLE  STAR  in  the  body  of  the  figure;  R.  A.  16h.  lira.  28s.; 

gers  ?  Egyptian  myth  respecting  Typhon,  &c.  ?  Supposed  reason  why  Scorpio  was  placed 
where  it  u?  Why  do  astrologers  connect  Mars  with  Scorpio ?  The  Alchemists?  Wha*, 
poetic  proof  of  the  itiquity  of  Scorpio?  Ovid's  myth  respecting  ?  Relative  position  of 
Orion  and  Scorpio.'1  £ '<vce  of  Scorpio  in  the  Hebrew  Zodiac,  and  why? 

TKLSSCOPIC  OBJECTS.— Alpha?  Beta?  Nu?  Sigma?  Whatcluster?  Point  out  on  the 
•nap.  What  Nebula  ? 


HERCULES.  103 

l»ec.  b.  26*  12' 2*.     About  2*  west   by  north  of  Antares.    A  4,  creamy  white;  B  9H 
lilac  tint. 

5.  A  COMPRESSED  GLOBULAR  CLUSTER  in  the  right  foot  of  Ophiuchus,  or  the    Scorpion'? 
back  ;  R.  A.  16h.  07m.  28s. ;  Dec.  S.  22°  35'  4".    Half  way  between  a  and  ,<3  Scorpii,  or  V 
east  of  (5.    A  fine  bright  object,  in  an  open  space,  with  a  few  telescopic  stars  in  the 
field.    Pronounced  by  Herschel  "  the  richest  and  most  condensed  mass  of  stars  which 
the  firmament  can  offer  to  the  contemplation  of  astronomers."    Map  IX.,  Fig".  52. 

6.  A  compressed  mass  of  very  small  stars,  in  the  middle  of  the  body,  with  outlay  re, 
and  a  few  stellar  companions  in  the  field ;  R.  A.  16h.  13m.  51s. ;  Dec.  S.  26°  07'  5'.    It  is 
l%°  west  of  Antares.    Elongated  and  bright  in  the  center. 

7.  A  fine  large  RESOLVABLE  NEBULA  at  the  root  of  the  tail,  about  7°  southeast  from 
Antares  ;  R.  A.  16h.  51m.  04s. ;  Dec.  S.  29°  50'  6".    A  mass  of  small  stars  running  up  to  a 
blaze  in  the  center — has  been  mistaken  for  a  comet. 


HERCULES.— MAP  V. 

203.  Hercules  is  represented  on  the  map  invested  with  the 
skin  of  the  Nemaean  Lion,  holding  a  massy  club  in  his  right 
hand,  and  the  three-headed  dog  Cerberus  in  his  left.     He  occu 
pies  a  large  space  in  the  northern  hemisphere,  with  one  foot  rest- 
ing on  the  head  of  Draco,  on  the  north,  and  his  head  nearly 
touching  that  of  Ophiuchus,  on  the  south.     This  constellation 
extends  from  12°  to  50°  north  declination,   and  its  mean  right 
ascension,  is  255°  ;  consequently  its  centre  is  on  the  meridian 
about  the  21st  of  July. 

204.  Hercules  is  bounded  by  Draco  on  the  north,  Lyra  on  the 
east,  Ophiuchus  or  the  Serpent-Bearer  on  the  south,  and  the  Ser- 
pent and  the  Crown  on  the  west.     It  contains  one  hundred  and 
thirteen  stars,  including  one  of  the  2d,  or  of  between  the  2d  and 
3d  magnitudes,  nine  of  the  3d  magnitude,  and  nineteen  of  the 
4th.    The  principal  star  is  Ras  Algethi,  and  is  situated  in  the 
head,    about   25°  southeast  of   Corona   Borealis.     It    may  be 
readily  known  by  means  of  another  bright  star  of  equal  magni- 
tude, 5°  east-southeast  of  it,  called  Ras  Alhague.    Ras  Alhague 
marks  the  head  of  Ophiuchus,  and  Ras  Algethi  that  of  Her- 
cules.    These  two  stars  are  always  seen  together  like  the  bright 
pairs  in  Aries,  Gemini,  the  Little  Dog,  &c.     They  come  to  our 
meridian  about  the  28th  of  July,  near  where  the  sun  does  the 
last  of  April,  or  the  middle  of  August. 

About  midway  between  Ras  Algethi  on  the  southeast,  and  Ariadne's  Crown  on  t,ie 
northwest,  may  be  seen  Beta  and  Gamma,  two  stars  of  the  3d  magnitude,  situated  in 
the  west  shoulder,  about  3°  apart.  The  northernmost  of  these  two  is  called  RifUUdU, 

Those  four  stars  in  the  shape  of  a  diamond,  8°  or  10*  southwest  of  the  two  in  the 
shoulder  of  Hercules,  are  situated  in  the  head  of  the  Serpent. 


203.  Describe  Hercules?  His  magnitude  and  position?  When  on  the  meridian  Y 
204.  How  bounded  ?  Number  of  stars  ?  Their  size  ?  Principal  star,  and  how  knowu  ? 
What  said  of  Ras  Alhague,  and  Ras  Algethi  ?  Of  Beta  aud  Gamma  ? 


104  ASTRONOMY. 

205.  About  12°  E.  N.  E.  of  Rutilicus,  and  10£°  directly  north  o 
Has  Algethi,  are  two  stars  of  the  4th  magnitude,  in  the  east 
shoulder.  They  may  be  known  by  two  very  minute  stars  a  little 
above  them  on  the  left.  The  two  stars  in  each  shoulder  of  Her 
cules,  with  Ras  Algethi  in  the  head,  form  a  regular  triangle. 

The  left,  or  east  arm  of  Hercules,  which  grasps  the  triple-headed  monster  Cerberus, 
may  be  traced  by  means  of  three  or  four  stars  of  the  4th  magnitude,  situated  in  a  ro\v, 
8°  and  4°  apart,  extei  ding  from  the  shoulder,  in  a  northeasterly  direction.  That  small 
cluster,  situated  in  a  triangular  form,  about  14"  northeast  of  Ras  Algethi,  and  18*  east- 
eoutheast  of  the  left  shoulder,  distinguish  the  head  of  Cerberus. 

Eighteen  or  20°  northeast  of  the  Crown,  are  four  stars  of  the  3d  and  4th  magnitudes, 
forming  an  irregular  square,  of  which  the  two  southern  ones  are  about  4°  apart,  and  in 
a  line  6°  or  7°  south  of  the  two  northern  ones,  which  are  nearly  7°  apart. 

Pi,  in  the  northeast  corner,  maybe  known  by  means  of  one  or  two  other  small  stars, 
close  by  it,  on  the  east.  Eta,  in  the  northwest  corner,  may  be  known  by  its  being  in  a 
row  with  two  smaller  stars,  extending  toward  the  northwest,  and  about  4°  apart.  The 
stars  of  the  4th  magnitude,  just  south  of  the  Dragon's  head,  point  out  the  left  foot  and 
ankle  of  Hercules. 

Several  other  stars,  of  the  3d  and  4th  magnitudes,  may  be  traced  out  in  this  constella- 
tion, by  reference  to  the  map. 

HISTORY. 

This  constellation  is  intended  to  immortalize  the  name  of  Hercules,  the  Theban^  so 
celebrated  in  antiquity  for  his  heroic  valor  and  invincible  prowess.  According  to  the 
ancients,  there  were  many  persons  of  this  name.  Of  all  these,  the  son  of  Jupiter  and 
Alcmena  is  the  most  celebrated,  and  to  him  the  actions  of  the  others  have  been  gene- 
rally attributed. 

The  birth  of  Hercules  was  attended  with  many  miraculous  events.  He  was  brought 
up  at  Tirynthus,  or  at  Thebes,  and  before  he  had  completed  his  eighth  month,  the  jealousy 
of  Juno,  who  was  intent  upon  his  destruction,  sent  two  snakes  to  devour  him.  Not  ter- 
rified at  the  sight  of  <he  serpents,  he  boldly  seized  them,  and  squeezed  them  to  death, 
while  his  brothei  Iphicles  alarmed  the  house  with  his  frightful  shrieks. 

He  was  early  instructed  in  the  liberal  arts,  and  soon  became  the  pupil  of  the  centaur 
Chiron,  under  whom  he  rendered  himself  the  most  valiant  and  accomplished  of  all  the 
heroes  of  antiquity.  In  the  18th  year  of  his  age,  he  commenced  his  arduous  and  glorious 
pursuits.  He  subdued  a  lion  that  devoured  the  flocks  of  his  supposed  father,  Amphi- 
tryon. After  he  had  destroyed  the  lion,  he  delivered  his  country  from  the  annual  tri- 
bute of  a  hundred  oxen,  which  it  paid  to  Erginus. 

As  Hercules,  by  the  will  of  Jupiter,  was  subjected  to  the  power  of  Eurystheus,  and 
obliged  to  obey  him  in  every  respect,  Eurystheus,  jealous  of  his  rising  fame  and  power, 
ordered  him  to  appear  at  Mycenae,  and  perform  the  labors  which,  by  priority  of  birth, 
he  was  empowered  to  impose  upon  him.  Hercules  refused,  but  afterwards  consulted 
the  oracle  of  Apollo,  and  was  told  that  he  must  be  subservient,  for  twelve  years,  to  the 
will  of  Eurystheus,  in  compliance  with  the  commands  of  Jupiter;  and  that,  after  he  had 
achieved  the  most  celebrated  labors,  he  should  be  reckoned  in  the  number  of  the  gods. 
So  plain  an  answer  determined  him  to  go  to  Mycenae,  and  to  bear  with  fortitude  what- 
ever gods  or  men  should  impose  upon  him.  Eurystheus,  seeing  so  great  a  man  totally 
subjected  to  him,  and  apprehensive  of  so  powerful  an  enemy,  commanded  him  to  achieve 
a  number  of  enterprises  the  most  difficult  and  arduous  ever  known,  generally  called  the 
TWELVE  LABORS  OF  HKRCULES.  Being  furnished  with  complete  armor  by  the  favor  of  the 
gods,  he  boldly  encountered  the  imposed  labors. 

1.  He  subdued  the  Nemaean  Lion  in  his  den,  and  invested  himself  with  his  skin. 

2.  He  destroyed  the  Lernaean  Hydra,  with  a  hundred  hissing  heads,  and  dipped  his 
arrows  in  the  gall  of  the  monster,  to  render  their  wounds  incurable. 

8.  He  took  alire  the  stag  with  golden  horns  and  brazen  feet,  so  famous  for  its  incre- 
dible swiftness,  after  pursuing  it  for  twelve  months,  and  presented  it,  unhurt,  to 
Eurystheus. 

4.  He  took  alive,  the  Erymanthian  Boar,  and  killed  the  Centaurs  who  opposed  him. 


2<>5.  What  two  other  stars,  and  what  triangle?  How  trace  the  left  or  east  arm  of  Her- 
cules? What  four  stirs,  and  forming  what?  Describe  Pi,  and  how  known.  Eta?  Any 
other  stars? 

HISTORY.— Design  of  tMs  constellation  ?    Story  of  the  birth  of  Hercules  ?    His  wondt:i  fu 


HERCULES.  105 

5.  He  cleansed  the  stables  of  Augias,  in  which  3,000  oxen  had  been  confined  for  many 
years. 

6.  He  killed  the  carnivorous  birds  which  ravaged  the  country  of  Arcadia,  and  fed  on 
human  flesh. 

7.  He  took  alive,  and  brought  into  Peloponnesus,  the  wild  bull  of  Crete,  which  no 
mortal  durst  look  upon. 

8.  He  obtained  for  Eurystheus  the  mares  of  Diomedes,  which  fed  on  human  flesh  after 
having  given  their  owner  to  be  first  eaten  by  them. 

9.  He  obtained  the  girdle  of  the  queen  of  the  Amazona,  a  formidable  nation  of  warlike 
f-  -rr>,les. 

10.  He  killed  the  monster  Geryon,  king  of  Gades,  and  brought  away  his  numerous 
flocks,  which  fed  upon  human  flesh. 

11.  He   obtained  the  golden  apples  from  the  garden  of  the  Hesperides,  which  were 
•*  \tchcd  by  a  dragon. 

"2.  And  finally,  he  brought  up  to  the  earth  the  three-headed  dog  Cerberus,  the  guar- 
dian of  the  entrance  to  the  infernal  regions. 

According-to  Dupuis,  the  twelve  labors  of  Hercules  are  only  a  figurative  representation 
of  the  annual  course  of  the  sun  through  the  twelve  signs  of  the  Zodiac ;  Hercules  being  put 
for  the  sun,  inasmuch  as  it  is  the  powerful  planet  which  animates  and  imparts  fecundity 
to  the  universe,  and  whose  divinity  has  been  honored,  in  every  quarter,  by  temples  and 
altars,  and  consecrated  in  the  religious  strains  of  all  nations. 

Thus  Virgil,  in  the  eighth  book  of  his  JSneid,  records  the  deeds  of  Hercules,  and  eele  • 
brates  his  praise  : — 

"  The  lay  records  the  labors,  and  the  praise, 

And  all  the  immortal  acts  of  Hercules. 

First,  how  the  mighty  babe,  when  swath'd  in  bands, 

The  serpents  strangled  with  his  infant  hands ; 

Then,  as  in  years  and  matchless  force  he  grew, 

The  (Echalian  walls  and  Trojan  overthrew, 

Besides  a  thousand  hazards  they  relate, 

Procured  by  Juno's  and  Eurystheus'  hate. 

Thy  hands,  unconquer'd  hero,  could  subdue 

The  cloud-born  Centaur,  and  the  monster  crew; 

Nor  thy  resistless  arm  the  bull  withstood ; 

Nor  he,  the  roaring  terror  of  the  wood. 

The  triple  porter  of  the  Stygian  seat 

With  lolling  tongue  lay  fawning  at  thy  feet, 

And,  seized  with  fear,  forgot  the  mangled  meat. 

The  infernal  waters  trembled  at  thy  sight: 

Thee,  god,  no  face  of  danger  could  affright; 

Nor  huge  Typhaeus,  nor  the  unnumber'd  snake, 

Increased  with  hissing  heads,  in  Lerna's  lake." 

Besides  these  arduous  labors  which  the  jealousy  of  Eurystheus  imposed  upon  him,  ne 
also  achieved  others  of  his  own  accord,  equally  celebrated.  Before  he  delivered  himself 
up  to  the  king  of  Mycenze  he  accompanied  the  Argonauts  to  Colchis.  He  assisted  the 
gods  in  their  wars  against  the  giants,  and  it  was  through  him  alone  t>at  Jupiter  obtained 
the  victory.  He  conquered  Laomedon  and  pillaged  Troy. 

At  three  different  times  he  experienced  fits  of  insanity.  In  the  second,  he  slew  the 
brother  of  his  beloved  lole ;  in  the  third  he  attempted  to  carry  away  the  sacred  tripod 
from  Apollo's  temple  at  Delphi,  for  which  the  oracle  told  him  he  must  be  sold  as  a  sla^e. 
He  was  sold  accordingly  to  Omphale,  que^n  of  Lydia,  who  restored  him  to  liberty,  and 
married  him.  After  this  he  returned  to  Peloponnesus,  and  re-established  on  the  throne 
of  Sparta  his  friend  Tyndarus,  who  had  been  expelled  by  Hippocoon.  He  became 
enamored  of  Dejanira,  whom,  after  having  overcome  all  his  rivals,  he  married:  but  wa? 
obliged  to  leave  his  father-in-law's  kingdom,  because  he  had  inadvertently  killed  a  man 
with  a  blow  of  his  fist.  He  retired  to  the  court  of  Ceyx,  king  of  Trachina,  and  in  his 
way  was  stopped  by  the  streams  of  the  Evenus,  where  he  slew  the  Centaur  Nessus,  for 

E resuming  to  offer  indignity  to  his  beloved  Dejanira.     The  Centaur,  on  expiring,  gave  to 
ejanira  the  celebrated  tunic  which  afterward  caused  the  death  of  Hercules.     "This 
tunic,"  said  the  expiring  monster,  "  has  the  virtue  to  recall  a  husband  from  unlawful 
love."    Dejanira,  fearing  lest  Hercules  should  relapse  again  into  love  for  the  beautifui 
lole,  gave  him  the  fatal  tunic,  which  was  so  infected  with  the  poison  of  the  Lernsean 

exploits  ?     Origin  and  character  of  the  twelve  labors  ?    What  are  these  labors  supposed 
to  represent?    What  quotation  from  Virgil  ?     Story  of  the  death  of  Hercules?    Ovid  * 


i06  ASTRONOMY. 

Hydra,  tnat  he  had  no  sooner  invested  himself  with  it,  than  it  began  tc  penetrate  his 
hones,  and  to  boil  through  all  his  veins.    He  attempted  to  pull  it  off,  but  it  was  too  lato. 
"  As  the  red  iron  hisses  in  the  flood, 
So  boils  the  venom  in  his  curdling  blood. 
Now  with  the  greedy  flame  his  entrails  glow, 
And  livid  sweats  down  all  his  body  fir/* 
The  crackling  nerves,  burnt  up,  are  burst  in  twain, 
The  lurking  venom  melts  his  swimming  brain." 

As  the  distemper  was  incurable,  he  implored  the  protection  of  Jupiter,  gave  his  bow 
and  arrows  to  Philoctetes,  and  erected  a  large  burning  pile  on  the  top  of  Mount  (Eta. 
He  spread  on  the  pile  the  skin  of  the  Nemaean  lion,  and  laid  himself  down  upon  it,  as  on 
a  bed,  leaning  his  head  upon  his  club.  Philoctetes  set  fire  to  .the  pile,  and  the  hero  saw 
himself,  on  a  sudden,  surrounded  by  the  most  appalling  flames;  yet  he  did  not  betray 
any  marks  of  fear  or  astonishment.  Jupiter  saw  him  from  heaven,  and  told  the  sur- 
rounding gods,  who  would  have  drenched  the  pile  with  tears,  while  they  entreated  tt  it 
he  would  raise  to  the  skies  the  immortal  part  of  a  hero  who  had  cleared  the  earth  frcm 
BO  many  monsters  and  tyrants  ;  and  thus  the  thunderer  spake : — 

"  Be  all  your  fears  forborne  : 

The  (Etean  fines  do  thou,  great  hero,  scorn. 

Who  vanquish'd  all  things  shall  subdue  the  flame 

That  part  alone  of  gross  maternal  frame 

Fire  shall  devour  ;  while  what  from  me  he  drew 

Shall  live  immortal,  and  its  force  subdue : 

That,  when  he's  dead,  I'll  raise  to  realms  above , 

May  all  the  powers  the  righteous  act  approve." 

Ovid's  Met.  lib.  ix. 

Accordingly,  after  the  mortal  part  of  Hercules  was  consumed,  as  the  ancient  poets 
say,  he  was  carried  up  to  heaven  in  a  chariot  drawn  by  four  horses. 

"  Quern  pater  omnipotens  inter  cava  nubila  raptum, 
Quadrijugo  curru  radiantibus  intulit  astris." 

"  Almighty  Jove 

In  his  swift  car  his  honor'd  offspring  drove ; 
High  o'er  th  e  hollow  clouds  the  coursers  fly, 
And  lodge  the  hero  in  the  starry  sky." 

Ovid's  Met.  lib.  ix.  v.  271. 

TELESCOPIC  OBJECTS. 

1.  a  HBRCULIS  (Ras  AlgetM)—A  beautiful  IX>UBLE  STAB  in  the  head  of  Hercules ;  R.  A. 
J7h.  07m.  21s. ;  Dec.  N.  14°  34'  05".    A  3J^,  orange  ;  B  5^,  greenish.     Map  VIII.,  Fig.  13. 

2.  (3  HBRCCLIS  (Rutibicus) — A  fine  DOUBLE  STAB  in  a  barren  field,  on  the  hero's  left 
Shoulder ;  R.  A.  16h.  23m.  21s. ;  Dec.  N.  21°  50'  6".    A  2}£,  pale  yellow;  B  11,  lilac  tint. 

8.  7  HERCULIS — An  open  DOUBLE  STAB  in  a  dark  field,  on  the  left  arm;  R.  A.  16h.  14m. 
63s.;  Dec.  N.  19°  32' 0".  A3j£,  silvery  white  ;  BIO,  lilac.  About  half-way  from  .Baa 
Algethi,  in  the  head,  to  Alphaeca  in  the  Northern  Crown. 

4.  6  HERCULIS — A  BINART  STAB  on  the  right  shoulder,  and  about  11°  due  north  of  a- 
R.  A.  17h.  08m.  28s.;  Dec.  N.  25°  01'  9".    A  4,  greenish  white;  B  S%,  grape  red.    It 
forms  an  equilateral  triangle  with  a  and  13. 

5.  C  HERCULIS — A  close  BINARY  STAB  over  the  middle  of  the  body ;  R.  A.  16h.  85m.  15s. , 
Dec.  N.  31°  53' 7".    A3,  yellowish  white;  B  6,  orange  tint.    A  "  wonderous  object"— • 
one  star  being  sometimes  occulted  by  the  other. 

6.  77  HEBCULIS — A  bright  star  with  a  distant  companion  on  the  left  thigh ;  R.  A.  16h. 
87m.  25s. ;  Dec.  N.  39°  13'  8".    A  3,  pale  yellow  ;  B  10,  dusky. 

7.  A  LARGE  CLUSTER  on  the  left  thigh,  between  £  and  rj,  5%'  southwesterly  of  the 
latter;  R.  A.  16h.  35m.  58s. ;  Dec.  N.  36°  45'  8".     A  superb  object,  blazing  up  in  the  cen- 
ter, with  numerous  outlayers.    Map  IX.,  Fig.  53.    May  be  seen  by  the  naked  eye  in  the 
absence  of  the  moon. 

8.  A  GLOBULAR  CLUSTER  of  minute  stars  1%°  north  by  east  of  f]  ;  R.  A.  17h.  12m.  14s  . 
Dec.  N.  43°  18'  4".    Large,  bright,  and  resolvable,  with  a   luminous  centre.    Several 
other  stars  in  the  field.    Map  IX.,  Fig.  '54. 

TELV.SCOPIC  OBJECTS.— Alpha  ?  Point  out  on  the  map  Beta?  Gamma?  Delta?  Zeta/ 
Eta?  What  clusters?  Point  out  on  the  map.  What  Nebula? 


SERPENTARIUS.  107 

9.  A  small  PLANETARY  NEBULA  between  the  hero's  shoulders  ;  R.  A.  16h.  37m.  46g. ;  Deo. 
9A°  05'  8*.    A  curious  object,  with  a  disc  8"  in  diameter.     Look  northeast  of  y  and  /3 
in  the  left  arm,  to  a  point  forming  an  equilateral  triangle  with  these  two  stars. 

10.  A  fine  PLANETARY  NEBULA  near  the  right  knee  of  Hercules;  R.  A.  16h.  43m.  28s.  • 
Dec.  N.  46°  47'  0".    About  4°  east  by  north  from  T.    It  is  large,  round,  and  of  a  lucid 
pa-e  blue  hue.    A  6th  magnitude  star  near  it  somewhat  eclipses  its  brightness 


SERPENTARIUS,  VEL  OPHIUCHUS  (THE  SERPENT  BEAEEE).— 
MAP  V. 

206.  THE  SERPENT-BEARER  is  also  called  JSsculapius,  or  the 
god  of  medicine.  He  is  represented  as  a  man  with  a  venerable 
beard,  having  both  hands  clenched  in  the  folds  of  a  prodigious 
serpent,  which  is  writhing  in  his  grasp. 

The  constellation  occupies  a  considerable  space  in  the  mid- 
heaven,  directly  south  of  Hercules,  and  west  of  Taurus  Pouia- 
towski.  Its  center  is  very  nearly  over  the  equator,  opposite  to 
Orion,  and  comes  to  the  meridian  the  26th  of  July.  It  contains 
seventy-four  stars,  including  one  of  the  2d  magnitude,  five  of 
the  3d,  and  ten  of  the  4th. 

207  The  principal  star  in  Serpentarius  is  called  Ras  Alhague, 
It  is  of  the  2d  magnitude,  and  situated  in  the  head,  about  5° 
E.  S.  E.  of  Ras  Algethi,  in  the  head  of  Hercules.     Has  Alhague 
is  nearly  13°  N.  of  the  equinoctial,  while  Rho,  in  the  southern 
foot,  is  about  25°  south  of  the   equinoctial.     These  two  stars 
serve  to  point  out  the  extent  of  the  constellation  from  north  to 
south.     Ras  Alhague  comes  to  the  meridian  on  the  28th  of  July, 
about  21  minutes  after  Ras  Algethi. 

About  10°  S.  W.  of  Ras  Alhague  are  two  small  stars  of  the  4th  magnitude,  scarcely 
more  than  a  degree  apart.  They  distinguish  the  left  or  west  shoulder.  The  northern 
one  is  marked  Iota  and  the  other  Kappa. 

Eleven  or  twelve  degrees  S.  S.  E.  of  Ras  Alhague  are  two  other  stars  of  the  3d  magni- 
tude, in  the  east  shoulder,  and  about  2*  apart.  The  upper  one  is  called  Cheteb,  and  the 
lower  one  Gamma.  These  stars  in  the  head  and  shoulders  of  Serpentarius,  form  a  tri- 
angle, with  the  vertex  in  Ras  Alhague,  and  pointing  toward  the  northeast. 

208  About  4°  E.  of  Gamma,  is  a  remarkable  cluster  of  four 
or  five  stars,  in  the  form  of  the  letter  Y,  with  tne  open  part  to 
the  north.     It  very  much  resembles  the  Hyades.     This  beautiful 
little  group  mark  the  face  of  TAURUS  PONIATOWSKI.     The  solsti- 
tial colure  passes  through  the  equinoctial  about  2°  E.  of  the 


206.  What  other  name  has  the  Serpent  Bearer?  How  represented?  Situation  and 
extent?  Number  and  size  of  its  principal  stars?  207.  Name  of  its  principal  star* 
M-ignitude  and  situation?  Rho,  and  its  situation?  Use  of  these  two  stars?  What  said 
of  Iota  and  Kappa?  Of  Chelcb  and  Gamma?  208.  What  remarkable  cluster?  Fn« 

5* 


108  ASTRONOMY. 

lower  star  in  the  vertex  of  the  Y.    The  letter  name  of  this 
star  is  k.  , 

There  is  something  remarkable  in  its  central  position.  It  is  situated  almost  exactly  fn 
the  mid-heavens,  being  nearly  equidistant  from  the  poles,  and  midway  between  the  ver- 
nal and  autumnal  equinoxes.  It  is,  however,  about  one  and  a  third  degrees  nearer  the 
north  than  the  south  pole,  and  about  two  degrees  nearer  the  autumnal  than  the  vernal 
equinox,  being  about  two  degrees  west  of  the  solstitial  colure. 

Directly  south  of  the  V,  at  the  distance  of  about  12°,  are  two  very  small  stars,  about 
2°  apart,  situated  in  the  right  hand,  where  it  grasps  the  serpent.  About  half-way 
between,  and  nearly  in  a  line  with,  the  two  in  the  hand  and  the  two  in  the  shoulder,  ie 
another  star  of  the  3d  magnitude,  marked  Zeta,  situated  in  the  Serpent,  opposite  the 
right  elbow.  It  may  be  known  by  means  of  a  minute  star  just  under  it. 

Marsic,  in  the  left  arm,  is  a  star  of  the  4th  magnitude,  about  10°  S.  W.  of  Iota  and 
Kappa.  About  7*  farther  in  the  same  direction  are  two  stars  of  the  3d  magnitude,  situ- 
ated in  the  hand,  and  a  little  more  than  a  degree  apart.  The  upper  one  of  the  two, 
which  is  about  16°  N.  of  G raffias  in  Scorpio,  is  called  Yed;  the  other  is  marked  Epsilon. 
These  two  stars  mark  the  other  point  in  the  folds  of  the  monster  where  it  is  grasped  by 
Serpentarius. 

The  left  arm  of  S-irpentarius  may  be  easily  traced  by  means  of  the  two  stars  in  the 
shoulder,  the  one  (Marsic)  near  the  elbow,  and  the  two  in  the  hand;  all  lying  nearly 
in  a  line  N.  N.  E.  and  S.  S.  W.  In  the  same  manner  may  the  right  arm  be  traced,  by 
stars  very  similarly  situated;  that  is  to  say,  first  by  the  two  in  the  east  shoulder,  just 
west  of  the  V,  thence  8°  in  a  southerly  direction  inclining  a  little  to  the  east,  by  Zeta, 
(known  by  a  little  star  right  under  it,)  and  then  by  the  two  small  ones  in  the  right  hand, 
situated  about  6°  below  Zeta. 

About  12*  from  Antarcs,  in  an  easterly  direction,  are  two  stars  in  the  right  foot,  about 
2°  apart.  The  largest  and  lower  of  the  two,  is  on  the  left  hand.  It  is  of  between  the 
8d  and  4th  magnitudes,  and  marked  Rho.  There  are  several  other  stars  in  this  constel- 
lation of  the  3d  and  4th  magnitudes.  They  may  be  traced  out  from  the  maps. 

"  Thee,  Serpentarius,  we  behold  distinct, 
With  seventy-four  refulgent  stars ;  and  one 
Graces  thy  helmet,  of  the  second  class  : 
The  Serpent,  in  thy  hand  grasp'd,  winds  his  spire 
Immense ;  fewer  by  ten  his  figure  trace ; 
One  of  the  second  rank  ;  ten  shun  the  sight; 
And  seven,  he  who  bears  the  monster  hides." — Eudosia. 

HISTORY. 

This  constellation  was  known  to  the  ancients  twelve  hundred  years  before  the  Chris- 
tian era.    Homer  mentions  it.    It  is  thus  referred  to  in  the  Astronomicon  of  Manillas  '- 
"  Next,  Ophiuchus  strides  the  mighty  snake, 
Untwists  his  winding  folds,  and  smooths  his  back, 
Extends  his  bulk,  and  o'er  the  slippery  scale 
His  wide-stretch'd  hands  on  either  side  prevail 
The  snake  turns  back  his  head  and  seems  to  rage : 
That  war  must  last  where  equal  power  prevails." 

JEsculapius  was  the  son  of  Apollo,  by  Coronis,  and  was  educated  by  Chiron  the  Ceii- 
taur  in  the  art  of  medicine,  in  which  he  became  so  skilful,  that  he  was  considered  the 
inventor  and  god  of  medicine.  At  the  birth  of  -.Esculapius,  the  inspired  daughter  of 
Chiron  uttered,  "  in  sounding  verse  "  this  prophetic  strain. 

"  Hail,  great  physician  of  the  world,  all  hail ! 
Hail,  mighty  infant,  who,  in  years  to  come, 
Shall  heal  the  nations  and  defraud  the  tomb! 
Swift  be  thy  growth !  thy  triumphs  unconfined ! 
Make  kingdoms  thicker,  and  increase  mankind  : 
Thy  daring  art  shall  animate  the  dead, 
And  draw  the  thunder  on  thy  guilty  head : 
Then  shalt  thou  die,  but  from  the  dark  abode 
Rise  up  victorious,  and  be  twice  a  god." 

and  resemblance?    Marks  what?    What  said  of  the  lower  star  in  the  V.?    What  stars 
Bouth  of  it  ?     What  c  f  Marsic  ?     Of  Yed  and  Epsilon  ?     How  trace  the  left  arm  ? 

HISTORT. — Antiquity  of  this  constellation  ?  Proof?  Who  was  JEsculapius  ?  Account 
of  his  great  skill  ?  His  metamorphosis  ?  Remarkable  fact  respecting  Socrates  and  Plato '• 


SERPENT  ARIL'S.  109 

He  accompanied  the  Argonauts  to  Colchis,  in  the  capacity  of  physician.  He  is  said  to 
ttave  restored  many  to  life,  insomuch  that  Pluto  complained  to  Jupiter,  that  hia  dark 
dominion  was  in  danger  of  being  depopulated  by  his  art. 

JSsculapius  was  worshiped  at  Epidaurus,  a  city  of  Peloponnesus,  and  hence  he  is 
styled  by  Milton  "  the  god  in  Epidaurus."  Being  sent  for  to  Rome  in  the  time  of  a  plague, 
he  assumed  the  form  of  a  serpent  and  accompanied  the  ambassadors,  but  though  thus 
changed,  he  was  -flSscuiapius  still,  in  serpente  deus — the  deity  in  a  serpent — and  under 
that  form  he  continued  to  be  worshiped  at  Rome.  The  cock  and  the  serpent  were  sacred 
to  him,  especially  the  latter.  The  ancient  physicians  used  them  in  their  prescriptions. 

One  of  the  last  acts  of  Socrates,  who  is  accounted  the  wisest  and  best  man  of  Pagan 
antiquity,  was  to  offer  a  cock  to  2Esculapius.  He  and  Plato  were  both  idolaters ;  they 
conformed,  and  advised  others  to  conform,  to  the  religion  of  their  country ;  to  gross 
fdolatry  and  absurd  superstition.  If  the  wisest  and  most  learned  were  so  blind,  what 
must  the  foolish  and  ignorant  have  been  ? 

TELESCOPIC  OBJECTS. 

1.  a  OPHIUCHI  (Ras  Alhague) — A  bright  star  with  a  minute  companion,  in  tne  head  of 
the  figure ;  R.  A.  ITh.  27m.  30s. ;  Dec.  N.  12°  40'  08".    A  2,  sapphire ;  B  9,  pale  grey.    A 
coarse  triplet  of  small  stars  near  them. 

2.  6  OPHIUCUI  (Yed) — A  star  with  a  distant  companion,  in  the  right  hand  ;  R.  A.  16h. 
05in.  58s. ;  Dec.  S.  3°  16'  07".    A  3,  deep  yellow  ;  B  10,  pale  lilac ;  a  third  minute  star  in 
the  field. 

3.  7)  OPHIUCHI — A  brilliant  star  with  a  distant  companion,  on  the  left  knee ;  on  the 
margin  of  the  milky  way ;  R.  A.  17h.  Olm.  13s. ;  Dec  N.  15°  81'  03".    A  2J$,  pale  yellow ; 
B  13,  blue. 

4.  T  OPHIUCHI — A  close  BINARY  STAR  on  the  left  hand,  15*  northeast  of  the  bright  star 
17,  just  described,  towards  Altair ;  R.  A.  17h.  54m.  22s. ;  Dec.  S.  8"  10'  04".    A  5,  and  B 
6-  both  pale  white ;  C  10,  light  blue ;  two  other  stars  in  the  field.    Out  of  place  on  the 
map,  or  R.  A.  wrong  in  the  tables,  as  given  above. 

5.  A  TRIPLE  or  rather  MULTIPLE  STAR,  between  the  left  foot  of  Ophiuchus,  and  the  root  of 
the  tail  of  Scorpio  ;  R.  A.  17h.  05m.  29s. ;  Dec.  S.  26°  21'  05".     It  is  about  10"  due  east  of 
Antares.     A  433,   ruddy;   B  6%,  pale  yellow;    0  7J4,  greyish.     The  latter  is  double,  a 
minute  companion  appearing  at  a  distance,  though  not  seen  through  ordinary  instruments. 
For  relative  position,  &c.,  see  Map  VIII.,  Fig.  14. 

6.  A  fine  GLOBULAR  CLUSTER,  between  the  right  hip  and  elbow ;  R.  A.  16h.  38m  56s. ; 
Dec.  S.  1°  40'  03".    A  rich  cluster,  condensed  towards  the  center,  ,with  many  straggling 
outlayers.     About  8*  from  £  Ophiuchi,  towards  ft. 

T.  A  RICH  CLUSTER  of  compressed  stars,  in  the  right  hip ;  R.  A.  16n.  48m.  45s. ;  Dec.  S. 
3°  51'  08".  About  8*  east  of  e  Ophiuchi;  or  half-way  between  /3  Librae,  and  a  Aquilae.  A 
oeautiful  round  cluster,  and  may  be  seen  with  a  telescope  three  feet  in  length. 

8.  A  BOUND  CLUSTER  on  the  left  leg ;  R.  A.  ITh.  09m.  42s. ;  Dec.  S.  18°  20'  07'.    It  lies 
about  3°  southeast  of  £,  and  rather  more  than  %  the  distance  on  a  line  from  Antares  tc 
Altair.    A  fine  object — myriads  of  stars  clustering  to  a  blaze  in  the  center. 

9.  A  LARGE  GLOBULAR  CLUSTER  in  the  left  arm ;  R.  A.  lib.  29m.  13s. ;  Deo.  S.  3'  09'  01'. 
It  lies  16°  south  of  Ras  Alhague,  or  about  half  way  from  0  Scorpii  to  t  Aquilae.    6%*  south- 
ty-west  of  y  Ophiuchi.    A  fine  object,  of  a  lucid  white,  and  may  be  seen  with  small  instru- 
aicnts.    Several  stars  in  the  field.    Map  IX.,  Fig.  55. 

TBLESCOPIC  OBJECTS.— Alpha?  Delta?  Eta?  What  multiple  star?  Point  out  on  the 
•nap.  What  clusters  ?  Which  shown  on  the  map? 


1  1  0  ASTRONOMY. 

CHAPTER  X. 

CONSTELLATIONS    ON   THE   MERIDIAN   IN   AUGFHT. 

DRACO  (THE  DEAGON).— MAP  VL 

209.  THIS  constellation,  which  compasses  a  large  circuit  in  the 
polar  regions  by  its  ample  folds  and  contortions,  contains  many 
stars  which  may  be  easily  traced.     From  the  head  of  the  mon- 
ster, which  is  under  the  foot  of  Hercules,  there  is  a  complete 
coil  tending  eastwardly,  about  17°  N.  of  Lyra  ;  thence  he  winds 
down  northerly  about  14°  to  the  second  coil,  where  he  reaches 
almost  to  the  girdle  of  Cepheus ;  then  he  loops  down  somewhat 
in  the  shape  of  the  letter  U,  and  makes  a  third  coil  about  15° 
below  the  first.     From  the  third  coil  he  holds  a  westerly  course 
for  about  13°,  then  goes  directly  down,  passing  between  the 
head  of  the  Lesser  and  the  tail  of  the  Greater  Bear. 

210.  Draco  contains  eighty  stars,  including  two  of  the  2d 
magnitude,  three  of  the  3d,  and  sixteen  of  the  4th. 

"  The  Dragon  next,  winds  like  a  mighty  stream : 
Within  its  ample  folds  are  eighty  stars, 
Four  of  the  second  order.    Far  he  waves 
His  ample  spires,  involving  either  Bear." 

The  head  of  the  Dragon  is  readily  distinguished  by  means  of 
four  stars,  3°,  4°,  and  5°  apart,  so  situated  as  to  form  an  irregu- 
lar square  ;  the  two  upper  ones  being  the  brightest,  and  both 
of  the  2d  magnitude.  The  right-hand  upper  one,  called  Etanin, 
has  been  rendered  very  noted  in  modern  astronomy  from  its 
connection  with  the  discovery  of  a  new  law  in  physical  science, 
called  the  Aberration  of  Light. 

The  letter  name  of  this  star  is  Gamma,  or  Gamma  Draconis  ;  and  by  this  appellation 
U  is  most  frequently  called.  The  other  bright  star,  about  4°  from  it  on  the  left,  is 
Rastdben. 

211.  About  4°  W.  of  Rastaben,  a  small  star  may,  with  close 
attention,  be  discerned  in  the  nose  of  the  Dragon,  which,  with 
the  irregular  square  before  mentioned,  makes  a  figure  somewhat 
resembling  an  Italic  V,  with  the  point  toward  the  west,  and  the 
open  part  toward  the  east.     The  small  star  in  the  nose,  is  called 
Er  Rakis. 

209.  Describe  Draco— its  situation  and  extent.  210.  Number  and  size  of  its  princi- 
pal stars?  How  may  the  head  of  Draco  be  distinguished?  What  said  of  Etanin?  Ita 
letter  name?  What  of  Rastaben?  211.  Of  Er  Rakis?  Further  of  Rastaben?  01 
Etanin  ?  Of  Grumium  ?  Of  Omicron  ?  How  may  the  second  coil  be  recognized  ?  What 
of  Zcta  ?  Of  Eta,  Theta,  and  Asich  ?  Of  Thuban,  Kappa,  and  Giansar  ? 


DRACO.  J  1  ] 

The  two  small  stars  5*  or  6°  S.  of  Rastaben  are  in  the  left  foot  of  Hercules* 

Raataben  is  on  the  meridian  nearly  at  the  same  moment  with  Ras  Alhague.  Etanin, 
40*  N.  of  it,  is  on  the  meridian  about  the  4th  of  August,  at  the  same  time  with  the  three 
western.stars  in  the  face  of  Taurus  Poniato^skii,  or  the  V.  It  is  situated  less  than  2°  west 
o  'the  solstitial  colure,  and  is  exactly  in  the  zenith  of  London.  Its  favorable  position  has 
lal  English  astronomers  to  watch  its  appearance,  for  loug  periods,  with  the  most  exact  and 
unwearied  scrutiny. 

Of  the  four  stars  forming  the  irregular  square  in  the  head,  the  lower  and  right-hand  one 
is  5J$*  N.  of  Etanin.  It  is  called  Q-rumiwn,  and  is  of  the  3d  magnitude.  A  few  degrees 
E.  of  the  square,  may  be  seen,  with  a  little  care,  eight  stars  of  the  5th  magnitude,  and  one 
of  the  4th,  which  is  marked  Omior&n,  and  lies  8  E.  of  Grumiura.  This  group  is  in  the  first 
coil  of  the  Dragon. 

The  second  coil  is  about  13°  below  the  first,  and  may  be  recognized  by  means  of  four 
stars  of  the  3d  and  4th  magnitudes,  so  situated  as  to  form  a  small  square,  about  half  the 
size  of  that  in  the  head.  The  brightest  of  them  is  on  the  left,  and  is  marked  Delta.  A  line 
drawn  from  Rastaben  through  Grumium,  and  produced  about  14°,  will  point  it  out.  A  line 
drawn  from  Lyra  through  Zi  Draconis,  and  produced  10*  further,  will  point  out  Zeta,  a 
star  of  the  3d  magnitude,  situated  in  the  third  coil.  Zeta  may  otherwise  be  known,  by  its 
being  nearly  in  a  line  with,  and  midway  between,  Etanin  and  Kochab.  From  Zeta,  the 
remaining  stars  in  this  constellation  are  easily  traced. 

Eta,  Theta,  and  Asich,  come  next ;  all  stars  of  the  3d  magnitude,  and  at  the  distance 
severally,  of  6°,  4°,  and  5"  from  Zeta.  At  Asich,  the  third  star  from  Zeta,  the  tail  of  the 
Dragon  makes  a  sudden  crook.  Thuban,  Kappa,  and  Giansar,  follow  next,  and  com- 
plete the  tail. 

212.  Teuton  is  a  bright  star  of  the  2d  magnitude,  11°  from 
Asich,  iu  a  line  with,  and  about  midway  between,  Mizar  and  the 
southernmost  guard  in  the  Little  Bear.  By  nautical  men  this 
star  is  called  the  Dragon's  Tail,  and  is  considered  of  much 
importance  at  sea.  It  is  otherwise  celebrated  as  being  formerly 
the, north  polar  star.  About  2,300  years  before  the  Christian 
Era,  Thuban  was  ten  times  nearer  the  true  pole  of  the  heavens 
than  Cynosura  now  is. 

Kappa  is  a  star  of  the  3d  magnitude,  10"  from  Alpha,  between  Megrez  and  the  pole. 
Mizar  and  Megrez,  in  the  tail  of  the  Great  Bear,  form,  with  Thuban  and  Kappa,  in  the 
tail  of  the  Dragon,  a  large  quadrilateral  figure,  whose  longest  side  is  from  Megrez  to 
Kappa. 

Giansar,  the  last  star  in  the  tail,  is  between  the  3d  and  4th  magnitudes,  and  5°  from 
Kappa.  The  two  pointers  will  also  point  out  Giansar,  lying  at  the  distance  of  little  more 
than  8°  from  them,  and  in  the  direction  of  the  pole. 

HISTORY. 

Mythologists  give  various  accounts  of  this  constellation.  By  some  it  Is  represented  as 
the  watchful  dragon  which  guarded  the  golden  apples  in  the  famous  garden  of  the  Hes- 
perides,  near  Mount  Atlas  in  Africa,  and  was  siain  by  Hercules.  Juno,  who  presented 
these  apples  to  Jupiter  on  the  day  of  their  nuptials,  took  Draco  up  to  heaven,  and  made  a 
constellation  of  him,  as  a  reward  for  his  faithful  services.  Others  maintain  that  in  the  war 
with  the  giants,  this  dragon  was  brought  into  combat,  and  opposed  to  Mineiva,  who  seized 
it  in  her  hand,  and  hurled  it,  twisted  as  it  was,  into  the  heavens  round  the  axis  of  the 
world,  before  it  had  time  to  unwind  its  contortions,  where  it  sleeps  to  this  day.  Other 
writers  of  antiquity  say,  that  this  is  the  dragon  killed  by  Cadmus,  who  was  ordered  by  hia 
father  to  go  in  quest  of  his  sister  Europa,  whom  Jupiter  had  carried  away,  and  never  tc 
return  to  Phenicia  without  her. 

"  When  now  Agenor  had  his  daughter  lost, 

He  sent  his  son  to  search  on  every  coast ; 

And  sternly  bade  him  to  his  arms  restore 

The  darling  maid,  or  see  his  face  no  more." 

214.  Size  and  position  of  Thuban?    What  called  by  nautical  men ?    Hew  otherwise 
celebrated?     What  further  of  Kappa,  M;/ar.  Megrez,  Ac.  ? 
HISTORY.— Various  Mythological  accounts?    Story  of  Cadmus  and  the  dragon's  teeth  V 


112  ASTRONOMY. 

Hi -i  search,  however,  proving  fruitless,  he  consulted  the  oracle  of  Apollo,  anl  TTM 
ordered  to  build  a  city  where  he  should  see  a  heifer  stop  in  the  grass,  and  to  call  tho 
country  Bceotia.  He  saw  the  heifer  according  to  the  oracle,  and  as  he  wished  to  render 
thanks  to  the  god  by  a  sacrifice,  he  sent  his  companions  to  fetcli  water  from  the  neighbor- 
ing grove.  The  waters  were  sacred  to  Mars,  and  guarded  by  a  most  terrific  dragon,  who 
devoured  all  the  messengers.  Cadmus,  tired  of  their  seeming  delay,  went  to  the  place, 
and  saw  the  monster  still  feeding  on  their  flesh. 

Cadmus,  beholding  such  a  scene,  boldly  resolved  to  avenge,  or  to  share  their  fate.  He 
therefore  attacked  the  monster  with  slings  and  ai'rows,  and,  with  the  assistance  of 
Minerva,  slew  him.  He  then  plucked  out  his  teeth,  and  sowed  them,  at  the  command  of 
Pallas,  in  a  plain,  when  they  suddenly  sprung  up  into  armed  men. 

Entertaining  worse  apprehension  from  the  direful  offspring  than  he  had  done  from  the 
dragon  himself,  he  was  about  to  fly,  when  they  fell  upon  each  other,  and  were  all  slain  in 
one  promiscuous  carnage,  except  five,  who  assisted  Cadmus  to  build  the  city  of  Bosotia. 

TELESCOPIC  OBJECTS. 

1.  a  DRACONIS  (Thubari) — A  star  with  a  distant  companion  in  the  fifth  coil  of  Draco  ;  R 
A.  14h.  00m.  03s. ;  Dec.  N.  65*  08'  04".    A  S%,  pale  yellow;  B  8,  dusky  ;  two  other  stars  In 
the  field.    Upwards  of  4,600  years  ago,  this  was  the  pole-star  of  the  Chaldeans. 

2.  3  DBACONIS  (Rastaberi) — A  star  with  a  very  distant  companion,  in  the  eye  of  Draco ; 
R.  A.  17h.  26m.  48s. ;  Dec.  N.  52*  25'  02'.    A  2,  yellow  ;  B  10,  bluish  ;  other  stars  in  field. 

3.  y  DRACONIS    (Etanin)—A  star  with  a  telescopic  companion,  in  the  crown  of  Draco ; 
R.  A.  17h.  52m.  53s. ;  Dec.  N.  51°  30'  06°.    A  2,  orange  tint ;  B  12,  pale  lilac.    A  third  star 
in  the  field  making  a  neat  triangle  with  A  and  B.     Etwnin  is  celebrated  as  the  star  by 
viewing  which,  Bradly  discovered  the  aberration  of  light  in  1725.    It  is  a  zenith-star  at 
the  Greenwich  observatory. 

4.  6  DRACONIS— A  bright  star  with  a  distant  companion,  in  the  second  flexure ;  R.  A. 
19h.  12m.  80s. ;  Deo.  N.  67'  22'  08'.    A  3,  deep  yellow  ;  B  9%,  pale  red ;  other  small  stars 
in  the  field. 

5.  e  DRACONIS — A  fine  double  star  between  the  second  and  third  flexures ;  R.  A.  19h. 
48m.  41s. ;  Dec.  N.  69°  51'  6".    A  5}$,  light  yellow;  B  8,  blue;    a  third  star  just  north 

Of    ft; 

6.  7}  DRACONIS— A  star  with  a  companion,  between  the  third  and-fourth  flexures  ;  R.  A 
I6h.  21m.  48s. ;  Dec.  N.  61*  52'  04".    A  3,  deep  yellow ;  B  11,  pale  grey. 

7.  jit  DRACONIS — A  very  neat  BINARY  SYSTEM,  on  the  tip  of  the  Dragon's  tongue  ;  R.  A 
17h.  02m.  02s.;   Dec.  N.  54°  41'  02".    A  4,  and  B  4%,  both  white.    Resembles  Castor, 
though'the  components  are  nearer  equal.     Period,  about  600  years. 

8.  A  TRIPLE  STAR  in  the  first  flexure;  R.  A.  18h.  21m.  36s.;  Dec.  N.  58°  42'  05".    A  5, 
pale  white;  B  8%,  light  blue;  C  7,  ruddy.    A  difficult  object— about  midway  between 
y  and  $. 

9.  A  beautiful  TRIPLE  STAR  in  the  nose  of  Draco,  on  a  line  from  y  over  ft,  and  near 
twice  as  much  further ;  R.  A.  16h.  32m.  28s. ;  Dec.  N.  53"  14'  09".    A  6,  pale  yellow ;  B  6>$, 
faint  lilac ;  C  6,  white  ;  four  other  stars  in  view. 

10.  A  BRIGHT-CLASS,  OVAL  NEBULA,  under  the  body  of  Draco ;  R.  A.  15h.  02m.  03s. ;  Dec. 
N.  56°  23'  0".     Faint  at  the  edges,  with  four  stars  in  the  field  ;  one  quite  near  it. 

11.  A  PLANETARY  NEBULA,  between  the  second  and  third  coil,  on  a  line  from  Polaris  to  y 
Draconis:  R.  A.  17h.  58m.  38s.;  Dec.  66°  38'  01".    A  remarkably  bright  and  pale  blue 
ob.iect,  with  several  telescopic  stars  in  the  field.    Map  IX.,  Fig.  56.    It  is  situated  exactly 
in  Hie  pole  of  Vie  ecliptic. 


LYRA  (THE  HARP).— MAP  Y. 

213.  This  constellation  is  distinguished  by  one  of  the  most 
brilliant  stars  in  the  northern  hemisphere.  It  is  situated  direct- 
ly south  of  the  first  coil  of  Draco,  between  the  Swan  on  the 

TELESCOPIC  OBJECTS.— Alpha ?  Beta?  Gamma?  Delta?  -Epsilon?  Eta?  Mu? 
Triple  stars ?  Nebulae? 

218.  TIow  is  Lyra  distinguished?  Where  situated?  Number  and  size  of  its  prfno% 
Jal  stars  ? 


LYRA.  113 

cast,  and  Hercules  on  the  west ;  and  when  on  the  meridian,  id 
almost  directly  overhead.  It  contains  twenty-one  stars,  includ- 
ing one  of  the  1st  magnitude,  two  of  the  3d,  and  as  many  of 
the  4th. 

There  Lyra,  for  the  brightness  of  her  stars, 
More  than  their  number,  eminent ;  thrice  seven 
She  counts,  and  one  of  these  illuminates 
The  heavens  far  around,  blazing  imperial 
In  the  first  order." 

214.  This  star  "  blazing  imperial  in  the  first  order"  is  called 
Vega,  and  sometimes  Wega ;  but  more  frequently,  Lyra,  after 
the  name  of  the  constellation. 

There  is  no  possibility  of  mistaking  this  star  for  any  other. 
It  is  situated  14f  °  S.  E.  of  Eltanin,  and  about  30°  N.  N.  E.  of 
Ras  Alhague  and  Has  Algethi.  It  may  be  certainly  known  by 
means  of  two  small,  yet  conspicuous  stars,  of  the  5th  magnitude, 
situated  about  2°  apart,  on  the  east  of  it,  and  making  with  it  a 
beautiful  little  triangle,  with  the  angular  point  at  Lyra. 

The  northernmost  of  these  two  small  stars  is  marked  ISpsilon,  and  the  southern  one 
Zeta.  About  2°  S.  E.  of  Zeta,  and  in  a  line  with  Lyra,  is  a  star  of  the  4th  magnitude, 
marked  Delta,  in  the  middle  of  the  Harp ;  and  4°  or  5°  S.  of  Delta,  are  two  stars  of  the 
8d  magnitude,  about  2°  apart,  in  the  garland  of  the  Harp,  forming  another  triangle,  whose 
vertex  is  in  Delta.  The  star  on  the  east  is  marked  Gamma  ;  that  on  the  west,  Beta.  If 
a  line  be  drawn  from  Etanin  through  Lyra,  and  produced  6°  farther,  it  will  reach  Beta. 

This  is  a  variable  star,  changing  from  the  3d  to  nearly  the  5th  magnitude  in  the  space 
of  a  week ;  it  is  supposed  to  have  spots  on  its  surface,  and  to  turn  on  its  axis,  like 
our  sun. 

Gamma  comes  to  the  meridian  21  minutes  after  Lyra,  and  precisely  at  the  same 
moment  with  EpsUon,  in  the  tail  of  the  Eagle,  17}$°  S.  of  it. 

The  remarkable  brightness  of  a  Lyra  has  attracted  the  admi- 
ration of  astronomers  in  all  ages.  Manillas,  who  wrote  in  the 
age  of  Augustus,  thus  alludes  to  it  : — 

*'  ONE,  placed  in  front  above  the  rest,  displays 
A  vigorous  light  and  darts  surprising  rays." 

Astronomicon,  B.  i.  p.  15. 

HISTORY. 

It  is  generally  asserted  that  this  is  the  celestial  Lyre  which  Apollo  or  Mercury  gave  to 
Orpheus,  and  upon  which  he  played  with  such  a  masterly  hand,  that  even  the  most  rapid 
rivers  ceased  to  flow,  the  wild  beasts  of  the  forest  forgot  their  wilduess,  and  the  moun- 
tains came  to  listen  to  his  song. 

Of  all  the  nymphs  who  used  to  listen  to  his  song,  Eurydyce  was  the  only  one  who  made 
a  deep  impression  on  the  musician,  and  their  nuptials  were  celebrated.  Their  happiness, 
however,  was  short.  Aristaeus  became  enamored  of  Eurydice,  and  as  she  fled  from  her 
pursuer,  a  serpent,  lurking  in  the  grass,  bit  her  foot,  and  she  died  of  the  wound.  Orpheus 
resolved  to  recover  her,  or  perish  in  the  attempt.  With  his  lyre  in  his  hand,  he  entered 
the  infernal  regions,  and  gained  admission  to  Pluto,  The  king  of  hell  was  charmed  with 
his  strains,  the  wheel  of  Ixion  stopped,  the  stone  of  Sisyphus  stood  still,  Tantalus  forgot 
his  thirst,  and  even  the  furies  relented. 

Pluto  and  Proserpine  were  moved,  and  consented  to  restore  him  Eurydice,  provided  he 
forbore  Jooking  behind  till  he  had  come  to  the  extremest  borders  of  their  dark  dominions. 

214.  Names  of  the  most  bnlliant  star?  How  certainly  known  ?  Where  are  KpdJen, 
Zeta,  Delta,  Gamma,  and  Beta?  What  peculiarity  about  B»ta  ?  In  a  Lyra:? 


. 

114  ASTRONOMY. 

The  condition  was  accepted,  and  Orpheus  was  already  in  sight  of  the  uppei  egions  of 
Jie  air,  when  he  forgot,  and  turned  back  to  look  at  his  long-lost  Eurydice.  He  saw  her, 
but  she  instantly  vanished  from  his  sight.  He  attempted  again  to  follow  her,  but  waa 
refused  admission. 

From  this  time,  Orpheus  separated  himself  from  the  society  of  mankind,  which  so 
offended  the  Thracian  women,  it  is  said,  that  they  tore  his  body  to  pieces,  and  threw  his 
head  into  the  Hebrus,  still  articulating  the  words  Eurydice  !  Eurydice!  as  it  was  carried 
down  the  stream  into  the  2Egean  sea.  Orpheus  was  one  of  the  Argonauts,  of  which  cele- 
brated expedition  he  wrote  a  poetical  account,  which  is  still  extant.  After  his  death,  he 
received  divine  honors,  and  his  lyre  became  one  of  the  constellations. 

This  fable,  or  allegory,  designed  merely  to  represent  the  power  of  music  in  the  hands 
of  the  great  master  of  the  science,  is  similarly  described  by  three  of  the  most  renowned 
Latin  poets.  Virgil,  in  the  fourth  book  of  hia  Georgics,  thus  describes  the  effect  of  ti.« 
lyre : — 

"  E'en  to  the  dark  dominions  of  the  night 

He  took  his  way,  through  forests  void  of  light, 

And  dared  amid  the  trembling  ghosts  to  sing, 

And  stood  before  the  inexorable  king. 

The  infernal  troops  like  passing  shadows  glide, 

And  listening,  crowd  the  sweet  musician's  side  ; 

Men,  matrons,  children,  and  the  unmarried  maid, 

The  mighty  hero's  more  majestic  shade, 

And  youth,  on  funeral  piles  before  their  parents  laid. 

E'en  from  the  depths  of  hell  the  damn'd  advance  ; 

The  infernal  mansions,  nodding,  seem  to  dance  ; 

The  gaping  three-mouth'd  dog  forgets  to  snari ; 

The  furies  hearken,  and  their  snakes  uncurl ; 

Ixion  seems  no  more  his  pain  to  feel, 

But  leans  attentive  on  his  standing  wheel. 

All  dangers  past,  at  length  the  lovely  bride 

In  safety  goes,  with  her  melodious  guide." 

Pythagoras  and  his  followers  represent  Apollo  playing  upon  a  harp  of  seven  strings, 
by  which  is  meant  (as  appears  from  Pliny,  b.  ii.  c.  22,  Macrobius  i.  c.  19,  and  Censorius 
c.  ii.),  the  sun  in  conjunction  with  the  seven  planets  ;  for  -they  made  him  the  leader  of 
that  septenary  chorus,  and  the  moderator  of  nature,  and  thought  that  by  his  attractive 
furce  he  acted  upon  the  planets  in  the  harmonical  ratio  of  their  distances. 

The  doctrine  of  celestial  harmony,  bj  which  was  meant  the  music  of  the  spheres,  was 
common  to  all  the  nations  of  the  East.  To  this  divine  music  Euripides  beautifully 
alludes : — "  Thee  I  invoke,  thou  self-created  Being,  who  gave  birth  to  Nature,  and  whom 
light  and  darkness,  and  the  whole  train  of  globes  encircle  with  eternal  music." — So  a.so 
bhakspeare : — 

"  Look,  how  the  floor  of  heaven 

Is  thick  inlaid,  with  patines  of  bright  gold  ; 

There's  not  the  smallest  orb  which  thou  behold'st, 

But  in  his  motion  like  an  angel  sings, 

Still  quiring  to  the  young-eyed  cherubim: 

Such  harmony  is  in  immortal  souls ; 

But,  while  this  muddy  vesture  of  decay 

Doth  grossly  close  it  in,  we  cannot  hear  it." 

The  lyre  was  a  famous  stringed  instrument,  much  used  among  the  ancients,  said  to 
have  been  invented  by  Mercury  about  the  year  of  the  world  2,000  ;  though  some  ascribe 
the  invention  to  Jubal.  (Genesis  iv.  21.)  It  is  universally  allowed,  that  the  lyre  was  the 
first  instrument  of  the  string  kind  ever  used  in  Greece.  The  different  lyres,  at  various 
periods  of  time,  had  from  four  to  eighteen  strings  each.  The  modern  lyre  is  the  Welsh 
harp.  The  lyre,  among  painters,  is  an  attribute  of  Apollo  and  the  Muses. 

All  poetry,  it  has  been  conjectured,  was  in  its  origin  lyric;  that  is,  adapted  to  recita- 
tion or  song,  with  the  accompaniment  of  music,  and  distinguished  by  the  utmost  boldness 
of  thought  and  expression ;  being  at  first  employed  in  celebrating  the  praises  of  gods 
and  heroes. 

Lesbos  was  the  principal  seat  of  the  Lyric  Muse;  and  Terpander,  a  native  of  this 
island,  who  flourished  about  650  years  B.  C.,  is  one  of  the  earliest  of  the  Lyric  poets 
whose  name  we  find  on  record.  Sappho,  whose  misfortunes  have  united  with  her  taleuts 
to  render  he<  name  memorable,  was  born  at  Mitylene,  the  chief  city  of  Lesbos.  She  wan 

HISTORY.— Story  of  Orpheus  and  Eurydice  ?  Design  of  this  myth  ?  Celebrated  b/  wha> 
poets  ?  Origin  of  the  Lyre,  and  of  Lyric  poetry  ?  What  said  of  Pindar  ? 


TAURUS    PONiATOWSKII.  Uo 

reckoned  a  tenth  muse,  and  placed  without  controversy  at  the  head  of  the  female  writers 
in  Greece.  But  Pindar,  a  native  of  Thebes,  who  flourished  about  500  years  B.  C.,  is 
styled  the  prince  of  lyric  poets.  To  him  his  fellow-citizens  erected  a  monument ;  and 
vhen  the  Lacedemonians  ravaged  Boeotia,  and  burnt  the  capital,  the  following  words 
were  written  upon  the  door  of  the  poet:  FOKBEAR  TO  BURN  THIS  HOUSE.  IT  WAS  THH 

DWELLING  OF  PlNDAR. 

TELESCOPIC    OBJECTS. 

1.  a  LYR^E— A  star  with  a  little  companion  ;  R.  A.  18h.  31m.  80s. ;  Dec.  N.  38°  38'  01*. 
A  1,  pale  sapphire  ;  B  11,  smalt  blue.    Map  VIII.,  Fig.  15. 

a  Lyria  is  computed  to  be  400,000  times  as  remote  as  our  sun;  or  38,000,000,000,000 
distant !  And  yet  what  is  this  to  the  mean  distances  of  many  of  those  of  the  12th  to  15tU 
magnitudes  ? 

2.  (3  LYR^E— A  star  with  its  companions  forming  a  quadruple  system ;  R.  A.  18h.  44ra. 
09s.;  Dec.  N.  33°  10'  08'.    A  3,  very  white  and  splendid;   B  8,  pale  grey;   0  8^,  faint 
yellow ;  D  9,  light  lilac,    ft  is  regarded  as  variable. 

8.  y  LYR.E — A  lustrous  star  7°  southeast  of  Vega,  with  a  minute  distant  companion  ' 
R.  A.  18h.  52m.  57s. ;  Dec.  N.  32°  28'  05".  A  3,  bright  yellow  ;  B  11,  blue  ;  other  tele- 
Bcopic  stars  in  the  field. 

4.  e  ~LYRJE — A  splendid  MULTIPLE  STAR,  only  1%°  northeast  of  Vega;  R.  A.  18h.  89m. 
02s. ;  Dec.  N.  39°  30'  03".    Map  VIII.,  Fig.  16.    With  small  instruments  it  appears  simply 
double  ;  but  with  better  instruments  each  of  the  components  are  found  to  be  double,  and 
binary  systems.    Between  the  twin  systems  are  three  minute  stars.    The  components  of 
the  two  systems  are  described  as  A  5,  yellow;  B  6%,  ruddy;  C  5,  and  D  53£,  both  white. 
A,  B  are  the  lowest,  or  northern  pair. 

These  two  twin  systems  are  in  motion  around  a  common  center  of  gravity,  as  well  as 
the  respective  components  around  each  other.  The  period  of  the  individual  systems  is 
estimated  at  about  2,i»00  years;  while  1,000,000  of  years  are  supposed  to  be  requisite  for 
a  revolution  round  the  common  center  of  both  ! 

5.  £  LYR^E — A  fine  DOUBLE  STAR  about  2°  south  of  e ;  R.  A.  ISh.  39m.  15s. ;  Dec.  N.  37* 
26'  05".    A  5,  topaz  ;  B  5%,  greenish. 

6.  n  LYRJE— A  neat  DOUBLE  STAR  6°  east  of  Vega;  R.  A.  19h.  08m  18s. ;  Dec.  N.  38°  52 
05".    A  5,  sky  blue  ;  B  9,  violet  tint.    A  fine  object  for  a  moderate  telescope. 

7.  v  LYR^E — A  QUADRUPLE  STAR  in  the  cross-piece  of  the  Lyre ;  R.  A.  ISh.  43m.  48s. ;  Dec. 
N.  32°  38  0".    A  9,  pale  yellow;  B  13,  bluish;  C  11,  pale  blue ;  D  15,  blue;  three  other 
Itars  in  the  field.    A  very  delicate  object. 

8.  A  GLOBULAR  CLUSTER,  in  a  splendid  field,  between  the  eastern  yoke  of  Lyra  and  the 
head  of  Cygnus ;  R.  A.  19h.  10m.  19s, ;  Dec.  N.  29°  54'  02\    About  5%°  southeast  of  /3  Lyrae, 
towards  (3  Cygni,  and  3%"  from  the  latter.    Map  IX.,  Fig.  57. 

9.  An  ANNULAR  NEBULA  between  (3  and  y ;  R.  A.  ISh.  47m.  37s.;  Dec.  N.  82*  50'  01". 
A  wonderful  object,  in  the  form  of  an  elliptical  ring.    Supposed  by  Herschel  to  be  900 
times  as  distant  as  Sirius.    A  clear  opening  through  its  center,  and  several  stars  in  tho 
field.    Map  IX.,  Fig.  58. 


TAURUS  PONIATOWSKII.— MAP  V. 

215.  This  small  asterism  is  between  the  shoulder  of  Ophiu- 
chus  and  the  Eagle.  The  principal  stars  are  in  the  head,  and 
of  the  4th  magnitude.  They  are  arranged  in  the  form  of  the 
letter  V,  and  from  a  fancied  resemblance  to  the  zodiac  Bull,  and 
the  Hyades^  became  another  Taurus.  See  description  of  Ser- 
pentarius,  article  206. 

TELESCOPIC  OBJECTS.— Alpha ?  Beta?  Gamma?  Epsilon?  Point  out  on  the  map, 
Zeta?  Eta?  Nu?  What  cluster?  Point  out  on  the.  map.  What  nebula,  and  where 
<)und  on  the  map? 

215.  Describe  Taurus  Poniatowskii.    Where  situated  ? 


1.16  ASTRONOMY. 

TELESCOPIC  OBJECTS. 

1.  A  neat  DOUBLE  STAR  in  the  space  between  the  Polish  Bull,  and  the  Eagle's  wing,  tt 
cast  of  a  Ophiuchi,  in  a  line  towards  Altair ;  R.  A.  17h.  58m.  17s. ;  Dec.  N.  11*  59'  OS" 
A  8,  straw-color;  B  8%,  sapphire  blue. 

2.  A  fine  PLANETARY  NEBULA,  in  a  rich  vicinity,  in  the  shoulder;  R.  A.  18h.  04m.  21s. , 
Dec.  N.  6*  49'  02*.    A  small  but  bright  object,  regarded  by  Prof.  Strure  as  one  of  the  motr 
curious  in  the  heavens.    Many  telescopic  stars  in  the  field. 


SCUTUM  SOBIESKI  (SOBIESKI'S  SHIELD). — MAP  Y. 

216.  This  small  figure  is  between  the  head  of  the  Polish  Bull, 
and  the  head  of  Sagittarius.  Its  four  principal  stars  are  of  the 
5th  magnitude  ;  and  it  is  important  chiefly  for  its  Telescopic 
Objects. 

TELESCOPIC  OBJECTS. 

1.  A  DOUBLE  STAR  l%"  northeast  of  fj.  Sagittarii;  R.  A.  ISh.  07m.  37s.;  Dec.  S.  19'  56' 
05".    A  8%,  and  B  10,  both  grey. 

2.  A  nea*  DOUBLE  STAR,  in  a  long  and  straggling  assemblage  below  the  Shield ;  R.  A. 
18h.  10m.  36s. ;  Dec.  S.  17°  11'  07".    A  9,  and  B  11.  both  bluish.    It  is  4*  from  /z  Sagittarii, 
in  a  very  rich  vicinity ;  several  splendid  fields  lying  only  about  1"  south  of  it. 

8.  A  BEAUTIFUL  CLUSTER  below  the  base  of  the  Shield ;  R.  A.  18h.  08m.  49s. ;  Dec.  S.  18* 
27'  05".  A  line  from  a  Aquilae,  southwest  over  /I  Antinoi,  and  continued  as  far  again, 
will  reach  this  object. 

4.  A  'SCATTERED  BUT  LARGE  CLUSTER,  north-half-east  from  fj.  Sagittarii  7" ;  R.  A.  18h. 
09m.  44s. ;  Dec.  S.  13°  50'  05".    Stars  disposed  in  pairs,  the  whole  forming  a  very  pretty 
object  in  a  telescope  of  tolerable  capacity. 

5.  A  HORSE-SHOE  NEBULA  just  below  the  Shield ;  R.  A.  18h.  llm.  23s. ;  Dec.  S.  16°  15'  08". 
It  has  been  compared  to  a  Greek  G.    Map  IX.,  Fig.  59.    Five  stars  in  the  object,  and 
others  in  the  field,  and  the  region  around  it  particularly  rich.    Sir  William  Herschel 
computed  that  there  were  285,000  stars  in  a  space  10°  long,  and  2}£*  wide;  many  of 
which  were  2,300  times  as  far  off  as  Siriujs ! 


SAGITTAEIUS  (THE  AECHEE).— MAP  V. 

21 1.  This  is  the  ninth  sign  and  the  tenth  constellation  of  the 
Zodiac.  It  is  situated  next  east  of  Scorpio,  with  a  mean  decli- 
nation of  35°  S.,  or  12°  below  the  ecliptic.  The  sun  enters  this 
sign  on  the  22d  of  November,  but  does  not  reach  the  constel- 
lation before  the  7th  of  December.  It  occupies  a  considerable 
space  in  the  southern  hemisphere,  and  contains  a  number  of  sub- 
ordinate, though  very  conspicuous  stars.  The  whole  number  of 
its  visible  stars  is  sixty-nine,  including  five  of  the  3d  magnitude, 
and  ten  of  the  4th. 

TELESCOPIC  OBJECTS.— What  double  star  ?    What  nebula  ? 

21  tf.  Situation  and  components  of  Scotum  Sobieski?    For  what  chiefly  important  ¥ 
TELESCOPIC  OBJECTS. — What  double  stars ?     Clusters?    Nebula? 

217.  Order  of  Sagittarius,  in  the  signs  and  constellations?    When  does  the  ouu  into, 
this  sign  f    The  conztcdation  T    Its  extent?    Number  and  size  of  its  stars  ? 


SAGITTARIUS.  lU 

218.  Sagittarius  may  be  readily  distinguished  by  means  of  five 
stars  of  the  3d  and  4th  magnitudes,  forming  a  figure  resem- 
bling a  little,  short,  straight-handled  dfpper,  turned  nearly  bot- 
tom upward,  with  the  handle  to  the  west,  familiarly  called  the 
Milk-Dipper,  because  it  is  partly  in  the  Milky-Way. 

This  little  figure  is  so  conspicuous  that  it  cannot  easily  be 
mistaken.  It  is  situated  about  33°  E.  of  Antares,  and  comes 
to  the  meridian  a  few  minutes  after  Lyra,  on  the  17th  of  Au- 
gust. Of  the  four  stars  forming  the  bowl  of  the  Dipper,  the  two 
upper  ones  are  only  3°  apart,  and  the  lower  ones  5°. 

The  two  smaller  stars  forming  the  handle,  and  extending  westerly  about  4J3*,  and  the 
easternmost  one  in  the  bowl  of  the  Dipper,  are  all  of  the  4th  magnitude.  The  star  in 
the  end  of  the  handle,  is  marked  Lambda,  and  is  placed  in  the  bow  of  Sagittarius,  just 
within  the  Milky- Way.  Lambda  may  otherwise  be  known  by  its  being  nearly  in  a  line 
with  two  other  stars  about  4M°  apart,  extending  toward  the  S.  E.  It  is  also  equidistant 
from  Pki  and  Delta,  with  which  it  makes  a  handsome  triangle,  with  the  vertex  in 
Lambda.  About  5°  above  Lambda,  and  a  little  to  the  west,  are  two  stars  close  together 
in  the  end  of  the  bow,  the  brightest  of  which  is  of  the  4th  magnitude,  and  marked  Mu. 
This  star  serves  to  point  out  the  winter  solstice,  being  about  ii°  N.  of  the  tropic  of  Capri- 
corn, and  less  than  one  degree  east  of  the  solstitial  colure. 

If  a  line  be  drawn  from  Sigma  through  Phi,  and  produced  about  6"  farther  to  the  west, 
it  will  point  out  Delta,  and  produced  about  3°  from  Delta,  it  will  point  out  Gfimma /  stars 
of  the  3d  magnitude,  in  the  arrow.  The  latter  is  in  the  point  of  the  arrow,  and  may  be 
known  by  means  of  a  small  star  just  above  it,  on  the  right.  This  star  is  so  nearly  on  the 
same  meridian  with  Etanin,  in  the  head  of  Draco,  that  it  culminates  only  two  minutes 
after  it. 

A  few  other  conspicuous  stars  in  this  constellation,  forming  a  variety  of  geometrical 
Ogures,  may  be  easily  traced  from  the  map. 

HISTORY. 

This  constellation,  it  is  said,  commemorates  the  famous  Centaur  Chiron,  son  of  Philyra 
and  Saturn,  who  changed  himself  into  a  horse,  to  elude  the  jealous  inquiries  of  his  wife 
Rhea. 

Chiron  was  famous  for  his  knowledge  of  music,  medicine  and  shooting.  He  taught 
mankind  the  use  of  plants  and  medicinal  herbs;  and  instructed,  in  all  the  polite  arts, 
the  greatest  heroes  of  the  age.  He  taught  ./Esculapius  physic,  Apollo  music,  and  Her 
cules  astronomy ;  and  was  tutor  to  Achille*,  Ason,  and  ^Eneas.  According  to  Ovid,  ho 
was  slain  by  Hercules,  at  the  river  Evenus,  for  offering  indignity  to  his  newly  marrie  1 
bride. 

"  Thou  monster  double  shap'd,  my  right  set  free — 
Swift  as  his  words,  the  fatal  arrow  flew; 
The  Centaur's  back  .admits  the  feather'd  wood,  v 
And  through  his  breast  the  barbed  weapon  stood; 
Which,  when  in  anguish,  through  the  flesh  he  tore, 
From  both  the  wounds  gush'd  forth  the  spumy  gore." 

The  arrow  which  Hercules  thus  sped  at  the  Centaur,  having  been  dipped  in  the  blood 
of  the  Lernaean  Hydra,  rendered  the  wound  incurable,  even  by  the  father  of  medicine 
himself,  and  he  begf^f  d  Jupiter  to  deprive  him  of  immortality,  if  thus  he  might  escape 
his  excruciating  paiu3.  Jupiter  granted  his  request,  and  translated  him  to  a  pla,cf 
among  the  constellations. 

"  Midst  golden  stars  he  stands  refulgent  now, 

And  thrusts  the  Scorpion  with  his  bended  bow." 

This  is  the  Grecian  account  of  Sagittarius ;  but  as  this  constellation  appears  on  the 
ancient  zodiacs  of  Egypt,  Dendera,  Esne,  and  India,  it  seems  conclusive  that  the  Greeks 

218.  How  distinguished?  Where  is  Lambda?  How  known?  Where  are  Mu,  Delta, 
and  Gamma  ? 

HISTORV. — What  does*  Sagittarius  commemorate  ?  Story  of  Chiron  ?  What  sii.il  of  the 
antiquity  of  this  constellation 


Ii8  ASTRONOMJf. 

only  borrowed  the  figure,  while  they  invented  tJie  fable.  This  is  knowc  to  be  trre  with 
respect  to  very  many  of  the  ancient  constellations.  Hence  the  jargon  of  the  conflicting 
accounts  which  have  descended  to  us. 

TELESCOPIC    OBJECTS. 

1.  fJ.  SAGITTARII — A  MULTIPLE  STAR  in  the  north  end  of  the  Archer's  bow ;  R.  A.  18h. 
04m.  11s. ;  Dec.  S.  21°  05'  07"    About  25*  east-northeast  of  An  tares.    A  3#,  pale  yellow; 
B  16,  blue  ;  C  9J<$,  and  D  10,  both  reddish. 

2.  a  SAGITTARII— A' star  with  a  distant  companion  in  the  Archer's  right  shoulder; 
R.  A.  ISh.  45m.  20s. ;  Dec.  S.  26°  29'  03'.    A  3,  ruddy ;  B  9  J$,  ash-colored. 

8.  A  very  delicate  TRIPLE  STAR,  between  the  heads  of  Sagittarius  and  Capricorn,  about 
25*  south-by-west  of  Altair,  and  10°  west  of  ^  Capricorn! ;  R.  A.  19h.  31m.  33s.;  Dec.  S. 
16°  .39'  02".  A  5%,  yellow ;  B  8,  violet ;  C  16,  blue.  Other  small  stars  in  the  field. 

4.  A  LARGE  AND  COARSE  CLUSTER  of  minute  stars,  close  to  the  upper  end  of  the  bow,  and 
In  the  Galaxy;  R.  A.  ISh.  03m.  08s. ;  Dec.  S.  21°  36'  01'.    Stars  of  the  10th  to  13th  mag- 
nitudes.   A  rich  field  of  no  particular  form. 

5.  A  LOOSE  CLUSTER  in  the  Galaxy,  between  the  Archer's  head  and  Sobieski's  Shield ; 
R.  A.  ISh.  22m.  14s. ;  Dec.  S.  19°  10'  02'.    The  most  prominent  are  a  pair  of  8th  magni- 
tude stars.    It  is  about  5°  northeast  of  jj,  Sagittarii. 

6.  A  FINE  GLOBULAR  CLUSTER  between  the  head  and  bow,  near  the  solsticial  colure ; 
R.  A.  ISh.  26m.  25s. ;  Dec.  S.  24°  01'  04".    A  fine  group,  compressed  towards  the  center, 
with  several  single  stars  in  the  field.    Map  IX.,  Fig.  60. 


CORONA  AUSTRALIS  (THE  SOUTHERN  CROWN).— MAP  V. 

219.  This  is  a  small  and  unimportant  constellation  near  the 
fore-legs  of  Sagittarius  ;  and  between  them  and  the  Milky-Way. 
R.  A.  about  18h.  44m.;  Dec.  S.  40°.     Its  four  principal  stars 
are  of  the  5th  magnitude,  situated  near  each  other,  and  arranged 
in  a  gentle  curve  line,  lying  north  and  south.     It  has  no  Mytho- 
logical History,  or  Telescopic  Objects  worthy  of  notice. 

%  t 

AQUILA  ET  ANTINOUS   (THE  EAGLE  AND  ANTINOUS).— MAP  Y. 

220.  This  double  constellation  is  situated  directly  south  of 
the  Fox  and  Goose,  and  between  Taurus  Poniatowskii  on  the 
west,   and  the  Dolphin  on  the  east.     It  contains  seventy-one 
stars,  including  one  of  the  1st  magnitude,  nine  of  the  3d,  arfd 
seven   of  the   4th.      It   may  be   readily  distinguished   by  the 
position  and  superior  brilliancy  of  its  principal  star. 

221.  Altair,  the  principal  star  in  the  Eagle,  is  of  the  1st,  or 
between  the  1st  and  2d  magnitudes.     It  is  situated  about  14° 

TELESCOPIC  OBJECTS.— Mu?     Sigma?     What  triple  star?     What  clusters?      Whicl 
shown  on  the  map?     Poiilt  it  out. 
219.  Describe  Corona  Australis.    Its  principal  stars  ?     History  and  Telescopic  Objects  V 

220.  Situation  of  Aquila  and  Antinous?       Number  and   size  of  its  principal  stars*1 

221.  Altair— how  known?    Stars  each  side  of  it?     Use  of  Altair  in  navigation?    Wha>. 


AQUILA   ET    ANTINOUS.  119 

S.  W.  of  the  Dolphin.  It  may  be  known  by  its  being  the 
largest  and  middle  one  of  the  three  bright  stars  which  are 
arranged  in  a  line  bearing  N.  W.  and  S.  E.  The  stars  on  each 
side  of  Altair  are  of  the  3d  magnitude,  and  distant  from  it  about 
2°.  This  row  of  stars  very  much  resembles  that  in  the  Guards 
of  the  Lesser  Bear. 

Altair  is  one  of  the  stars  from  which  the  moon's  distance  is 
taken  for  computing  longitude  at  sea.  Its  mean  declination  is 
nearly  8£°  N.,  and  when  on  the  meridian,  it  occupies  nearly  the 
same  place  in  the  heavens  that  the  sun  does  at  noon  on  the  12th 
day  of  April.  It  culminates  about  6  minutes  before  9  o'clock, 
on  the  last  day  of  August.  It  rises  acronically  about  the  begin- 
ning of  June. 

Ovid  alludes  to  the  rising  of  this  constellation ;  or,  more  probably,  to  that  of  the  prin- 
cipal star,  Altair : — 

"  Now  view  the  skies, 

And  you'll  behold  Jove's  hook'd-bill  bird  arise." 

Maasey's  Fasti. 

"  Among  thy  splendid  group 

ONE  dubious  whether  of  the  SECOND  RANK, 
Or  to  the  FIRST  entitled  ;  but  whose  claim 
Seems  to  deserve  the  FIRST." 

Eudosia. 

The  northernmost  star  in  the  line,  next  above  Altair,  is  called  Tarazed.  In  the  wing 
of  the  Eagle,  there  is  another  row  composed  of  three  stars,  situated  4°  or  5°  apart, 
extending  down  toward  the  southwest ;  the  middle  one  in  this  line  is  the  smallest,  being 
only  of  the  fourth  magnitude;  the  next  is  of  the  8d  magnitude,  marked  Delta,  and 
situated  8"  S.  W.  of  Altair. 

As  you  proceed  from  Delta,  there  is  another  line  of  three  stars  of  the  3d  magnitude, 
between  5°  and  6"  apart,  extending  southerly,  but  curving  a  little  to  the  west,  which 
mark.the  youth  Antinous.  The  northern  wing  of  the  Eagle  is  not  distinguished  by  any 
conspicuous  stars. 

Zeta  and  Epsilon,  of  the  Sd  magnitude,  situated  in  the  tail  of  the  Eagle,  are  about  2" 
apart,  and  12'  N.  W.  of  Altair.  The  last  one  in  the  tail,  marked  Epsilon,  is  on  the  same 
meridian,  and  culminates  the  same  moment  with  Gamma,  in  the  Harp. 

From  Epsilon,  in  the  tail  of  the  Eagle,  to  Theta,  in  the  wrist  of  Antinous,  may  be  tracel 
a  long  line  of  stars,  chiefly  of  the  3d  magnitude,  whose  letter  names  are  Theta,  Eta,  Mu, 
Zeta  and  Epsilon.  The  direction  of  this  line  is  from  S.  E.  to  N.  W.,  and  its  length  is 
about  25°. 

Eta  is  remarkable  for  its  changeable  appearance.  Its  greatest  brightness  continues 
but  40 hours;  it  then  gradually  diminishes  for  66  hours,  when  its  luster  remains  station- 
ary for  80  hours.  It  then  waxes  brighter  and  brighter,  until  it  appears  again  as  a  star 
of  the  3d  magnitude.  . 

From  these  phenomena,  it  is  inferred  that  it  not  only  has  spots  on  its  surface,  like  our 
sun,  but  that  it  also  turns  on  its  axis. 

Similar  phenomena  are  observable  in  Algol,  Beta,  in  the  Hare,  Delta,  in  Cepaeus,  and 
Omicron,  in  the  Whale,  and  many  others. 

"Aquila  the  next, 

Divides  the  ether  with  her  ardent  wing: 
Beneath  the  Swan  nor  far  from  Peffasufl, 
POETIC  EAGLB." 

pretic  quotation?    Where  are  Tarazed  and  Delta?     Zeta  and  Epsilon?    Theta?    Kbi 
For  what  remarkable  ? 


120  ASTRONOMY. 


HISTORY. 

Aquila,  or  the  Eagle,  is  a  constellation  usually  joined  with  Antinous.    Aquila  in  aur. 
posed  to  have  been  Merops,  a  king  of  the  island  of  Cos,  in  the  Archipelago,  and  the  hus- 
band of  Clymene,  the  mother  of  Phaeton  ;  this  monarch  having  been  transformed  into  an 
eagle,  and  placed  among  the  constellations.    Some  have  imagined  that  Aquila  was  the 
eagle  whose  form  Jupiter  assumed  when  he  carried  away  Ganymede ;  others,  that  it 
represents  the  eagle  which  brought  nectar  to  Jupiter  while  he  lay  concealed  in  the  cave  a*. 
Crete,  to  avoid  the  fury  of  his  lather,  Saturn.    Some  of  the  ancient  poets  say,  that  this 
is  the  eagle  which  furnished  Jupiter  with  weapons  in  his  war  with  the  giants  :  — 
"  The  towering  Eagle  next  doth  boldly  soar, 
As  if  the  thunder  in  his  claws  he  bore  ; 
He's  worthy  Jove,  since  he,  a  bird,  supplies 
The  heaven  with  sacred  bolts,  and  arms  the  skies." 

McmUius 

The  eagle  is  justly  styled  the  "sovereign  of  birds,"  since  he  is  the  largest,  strongest, 
and  swiftest  of  all  the  feathered  tribe  that  live  by  prey.  Homer  calU  the  eagle,  "  thts 
strong  sovereign  of  the  plumy  race  ;"  Horace  styles  him — 

"  The  royal  bird,  to  whom  the  king  of  heaven 
The  empire  of  the  feathered  race  has  given :" 

And  Milton  denominates  the  eagle  the  "  Bird  of  Jove."  Its  sight  Is  quick,  strong  and 
piercing,  to  a  proverb  :  Job  xxix.,  28,  &c. 

"  Though  strong  the  hawk,  though  practised  well  to  fly, 
An  eagle  drops  her  in  the  lower  sky ; 
An  eagle  when  deserting  human  sight. 
She  seeks  the  sun  in  her  unwearied  flight; 
Did  thy  command  her  yellow  pinion  lift 
So  high  in  air,  and  set  her  on  the  clift 
Where  far  above  thy  world  she  dwells  alone, 
And  proudly  makes  the  strength  of  rocks  her  own; 
Thence  wide  o'er  nature  takes  her  dread  survey, 
And  with  a  glance  predestinates  her  prey? 
She  feasts  her  young  with  blood  ;  and  hovering  o'er 
The  uuslaughtered  host,  enjoys  the  promise^  gore." 

ANTINOUS. 

A:  tinous  is  a  part  of  the  constellation  Aquili,  and  w«J  invented  by  Tycho  Brane 
Antinous  was  a  youth  of  Bithynia,  in  Asia  Minor.  So  greatly  was  his  death  lamented 
by  the  emperor  Adrian,  that  he  erected  a  temple  to  his  memory,  and  built  in  honor  of 
him  a  splendid  city,  on  the  banks  of  the  Nile,  the  ruins  of  which  are  still  visited  by 
travelers  with  much  interest. 

TELESCOPIC  OBJECTS. 

1.  a  AQUIL.B  (Altair) — A  bright  star  in  the  neck,  with  a  distant  companion ;  R.  A. 
19h.  42m.  58s. ;  Dec.  N.  8°  26'  09*.    A  1%,  pale  yellow;  B  10,  violet  tint. 

2.  13  AQUILA  (Alshairi)— A  DOUBLE  STAR,  also  in  the  neck  of  Aquila,  and  the  head  of 
Antinous;    R.  A.  19h.  47m.  26s.;  Dec.  N.  6°  00'  07".    About  2^°  south-southeast  of 
Altair.    A  3%,  pale  orange ;  B  10,  pale  grey  ;  with  other  stars  in  the  field. 

3.  y  AQUILA  (Tarazed)-A.  star  in  the  back  of  Aquila,  on  a  line  with  a  and  /?,  with  .1 
minute  companion  ;  R.  A.  19h.  38m.  38s. ;  Dec.  N.  10°  13'  06".    A  3,  pale  orange ;  B  12, 
dusky ;  other  stars  around. 

4.  6  AQUILA,  in  the  southern  wing ;   R.  A.  19h.  17m.  25s. ;   Dec.  N.  2'  48'  00'.    Has  a 
distant  companion.    A  3 J$,  white ;  B  12,  livid ;  other  stars  in  the  field. 

5.  £  AQUILA,  in  the  tail ;  R.  A.  18h.  58m.  02s. ;  Dec.  N.  13"  37'  08".    A  8,  greenish  tint; 
B  11,  livid ;  two  other  stars  in  the  field. 

6.  A  neat  DOUBLE  STAR  on  the  margin  of  the  lower  wing ;  R.  A.  ISh.  57m.  59s. ;  Dec.  N. 
6*  18'  08'.    A  7)6,  lucid  white ;  B  9,  cerulean  blue.     A  fine  object,  not  difficult  to  find,  aa 

HLSTORT. — Different  suppositions  respecting?  Manilius?  Horace?  Miltcn?  What 
s;iid  of  Antinous? 

TELESCOPIC  OBJECTS. — Alpha?     Beta?     Gamma?     Delta?    Xi?     Other  double 
\Vhatclustcrs?    Which  shown  on  the  map?     What  utbul;i? 


SAGITTA ANSER    ET    VULPECULA.  121 

It  lies  10*  due  noith  of  A  Antinoi,  a  3d  magnitude  star,  and  13*  west  of  /?  Aquilae.    The 
brul  cest  object  of  its  immediate  neighborhood. 

7.  A  WIDE  DOUBLE  STAR  about  4°  west-by-south  of  A  Antinoi,  between  the  foot  and 
Sobieski's  Shield  ;  R.  A.  ISh.  41m.  07s. ;  Dec.  S.  6°  05'  03".    A  7,  orange  tint;  B  9,  ceru- 
lean blue.    Many  telescopic  stars  in  the  field. 

8.  A  SPLENDID  CLUSTER  close  to  the  southeast  of  the  last  described  object;  R.  A.  ISh, 
12m.  32s. ;  Dec.  S.  6'  27'  02'.    It  is  between  the  left  foot  and  Sobieski's  Shield.    A  gor- 
geous object  "  somewhat  resembling  a  flight  of  wild  ducks  in  shape,"  has  an  8th  magni- 
tude star  in  the  middle,  and  two  larger  east  of  it ;  probably  all  three  between  us  and 
the  cluster.    Map  IX.,  Fig.  61. 

9.  A  LOOSE  CLUSTER  between  the  lower  wing  and  the  leg  of  Antinous,  and  13°  southwest 
3f  Altair,  on  a  line  from  Vega  through  e  Aquilae  ;  R.  A.  19h.  08m.  36s. ;  Dec.  S.  1°  11'  09" 
A  splashy  group  of  stars  from  the  9th  to  the  12th  magnitudes,  on  the  easteAi  margin  of 
the  Galaxy. 

10.  A  STELLAR  NEBULA  on  the  Eagle's  back,  about  5*  west  of  Altair;  R.  A.  19h.  23m. 
D5s. ;  Dec.  N.  8*  54'  01".    A  minute  object  in  the  Milky- Way ;  and  in  the  most  powerful 
telescopes,  fan-shaped. 


SAGITTA  (THE  AEEOW.)— MAP  Y. 

222.  SAGITTA  is  a  small  but  old  constellation  between  the 
Fox  and  Goose  on  the  north,  and  the  Eagle  on  the  south.  Its 
two  principal  stars  are  of  the  4th  magnitude,  and  lie  nearly  east 
and  west,  about  4°  apart.  The  next  two  largest  stars  are  of  the 
5th  magnitude. 

TELESCOPIC  OBJECTS. 

1.  £  SAGITTA— A  star  with  a  distant  companion  about  8*  north-northwest  of  Altair,  on 
a  line  towards  Vega;  R.  A.  19h.  30m.  03s. ;  Dec.  N.  16"  06'  5".    A  6,  pale  white ;  B  8, 
light  blue. 

2.  £  SAGITT^B — A  neat  DOUBLE  STAR  just  above  the  Arrow,  9"  south  by  east  from  ft 
Cygni,  and  10°  north  of  Altair;  R.  A.  19h.  41m.  53s.;  Dec.  N.  18°  44'  8".    A  5,  silvery 
white  ;  B  9,  blue. 

3.  •&.  SAGITT-B — A  TRIPLE  STAR  near  the  head  of  the  Arrow,  about  half-way  from  ft 
Cygni  to  a  Delphini ;  R.  A.  20h.  02m.  53s. ;  Dec.  N.  20°  26'  6'.  A  7,  pale  topaz ;  B  9,  grey  * 
C  8,  pearly  yellow. 

4.  A  RICH  COMPRESSED  CLUSTER  on  the  shaft  of  the  arrow,  10°  northeast  of  Altair 
R.  A.  19h.  46m.  36s. ;  Dec.  N.  18°  22'  1".    Telescopic  stars  around  it. 


AKSER  ET  VULPECULA  (THE  FOX  AND  GOOSE).— MAP  V. 

223.  This  is  a  modern  constellation,  situated  between  the 
Swan  on  the  north,  and  the  Arrow  or  the  Dolphin  and  Eagle  on 
the  south.  It  is  composed  of  some  thirty  stars,  the  largest  of 
which  is  of  the  3d  magnitude. 

TELESCOPIC  OBJECTS. 

1.  A  star  V7ith  a  distant  companion  on  the  nose  of  Reynard,  and  neck  of  the  Qooao 
B^°  south  of  ft  Cygni ;  R.  A.  19h.  22m.  08s. ;  Dec.  N.  24"  20'  J'. 


922.  Describe  Sagitta— its  principal  stars. 

TKLRSCOPIC  OBJECTS.— Epsilon?    Zeta?    What  triple  star?    Cluster V 

228.  Describe  the  Fox  and  Gx>o^.     Its  component  stars? 


ASTRONOMY. 

2.  A  WIDE  DOUBLE  STAR,  11  J$*  north  of  Altair,  between  the  Fox  and  the  Arrow,  in  tho 
eastern  edge  of  the  Galaxy;  R.  A.  19h.  46m.  20s.;  Dec.  N.  19°  65'  5".    A  and  B  both  7 
tnd  both  white. 

3.  A  LARGE  STRAGGLING  CLUSTER  on  the  neck  of  the  Goose,  and  about  3°  from  (3  Cygni;  R.  A 
19h.  20m.  30s. ;  Dec.  N.  24°  49'  3'.    Two  7th  magnitude  stars  in  the  west.    The  cluster 
has  the  form  of  a  Greek  Q.  t' 

4.  The  celebrated  DUMB-BKLL  NEBULA,  on  the  Fox's  breast,  about  7*  southeast  of  Cygni, 
and  nearly  half-way  between  it  and  the  Dolphin ;  R.  A.  19h.  52m.  39s. ;  Dec.  N.  22*  17'  1". 
(Map  IX.,  Fig.  62.)    This  magnificent  and  singular  object  is  in  a  crowded  vicinity,  where 
Cold  after  field  is  very  rich. 


CHAPTER   XI. 

CONSTELLATIONS    ON   THE   MERIDIAN   IN    SEPTEMBER. 

DELPHINUS  (THE  DOLPHIN).— MAP  V. 

224.  THIS  beautiful  little  cluster  of  stars  is  situated  13°  or 
1 4°  N.  E.  of  the  Eagle.     It  consists  of  eighteen  stars,  including 
four  of  the  3d  magnitude,  but  none  larger.     It  is  easily  distin- 
guished from  all  others,  by  means  of  the  four  principal  stars  in 
the  head,  which  are  so  arranged  as  to  form  the  figure  of  a  dia- 
mond, pointing  N.  E.  and  S.  W.     To   many,  this   cluster   is 
known  by  the  name  of  Job's  Coffin ;  but  from  whom,  or  from 
what  fancy,  it  first  obtained  this  appellation,  is  not  known. 

225.  There  is  another  star  of  the  3d  magnitude,  situated  in 
the  body  of  the  Dolphin,   about  3°  S.  W.  of  the  Diamond,  and 
marked  Epsilon.     The   other   four   are   marked   Alpha,    Beta, 
Gamma,  Delta.     Between  these  are  several  smaller  stars,  too 
small  to  be  seen  in  presence  of  the  moon. 

The  mean  decimation  of  the  Dolphin  is  about  15°  TsT.  It 
comes  to  the  meridian  the  same  moment  with  Deneb  Cygni,  and 
about  50  minutes  after  Altair,  on  the  16th  of  September. 

"  Thee  I  behold,  majestic  Cygnus, 
On  the  marge  dancing  of  the  heavenly  sea, 
Arion's  friend ;  eighteen  thy  stars  appear — 
One  telescopic." 

TELESCOPIC  OBJECTS. — What  double  stars ?    Cluster?    Nebula  ?     Point  out  on  the  map. 

224.  Constellations  in  this  chapter?  Delphinus?  Number  and  size  of  stars?  How 
aistiaguished?  What  other  name  has  this  constellation?  225.  Where  are  Epsilou, 
Alpha,  Beta,  Gamma  and  Delta?  Mean  declination,  Ac. 


HISTORY. 

The  DolpLm,  according  to  some  mythologists,  was  made  a  constellation  by  Neptunfa 
Decause  one  of  these  beautiful  fishes  had  persuaded  the  goddess  Ampliitrite,  who  had  made 
a  vow  of  perpetual  celibacy,  to  become  the  wife  of  that  deity ;  but  others  maintain,  that 
it  is  the  dolphin  which  preserved  the  famous  lyric  poet  and  musician  Arion,  who  was  a 
Dative  of  Lesbos,  an  island  in  the  Archipelago. 

He  went  to  Italy  with  Periander,  tyrant  of  Corinth,  where  he  obtained  immense  riches 
by  his  profession.  Wishing  to  revisit  his  native  country,  the  sailors  of  the  ship  in  whi;h 
he  embarked  resolved  to  murder  him,  and  get  possession  of  his  wealth.  Seeing  them 
immovable  in  their  resolution,  Arion  begged  permission  to  play  a  tune  upon  his  lute 
before  he  should  be  put  to  death.  The  melody  of  the  instrument  attracted  a  number  of 
dolphins  around  the  ship ;  he  immediately  precipitated  himself  into  the  sea ;  when  one 
of  them,  it  is  asserted,  carried  him  safe  on  his  back  to  Taenarus,  a  promontory  of  Laco- 
nia,  in  Peloponnesus  ;  when  he  hastened  to  the  court  of  Periander,  who  ordered  all  the 
Bailors  to  be  crucified  at  their  return. 

"  But  (past  belief),  a  dolphin's  arched  back 
Preserved  Arion  from  his  destined  wrack ; 
Secure  he  sits,  and  with  harmonious  strains 
Requites  his  bearer  for  his  friendly  pains." 

When  the  famous  poet  Hesiod  was  murdered  in  Naupactum,  a  city  of  JEtolia,  in  Greeae, 
and  his  body  thrown  into  the  sea,  some  dolphins,  it  is  said,  brought  back  the  floating 
corpse  to  the  shore,  which  was  immediately  recognized  by  his  friends ;  and  the  assassins 
being  afterwards  discovered  by  the  dogs  of  the  departed  bard,  were  put  to  death  by 
immersion  in  the  same  sea. 

Taras,  said  by  some  to  have  been  the  founder  of  Tarentum,  now  Tarento,  in  the  south 
of  Italy,  was  saved  from  shipwreck  by  a  dolphin  ;  and  the  inhabitants  of  that  city  pre- 
served the  memory  of  this  extraordinary  event  on  their  coin. 

The  natural  shape  of  the  dolphin,  however,  is  not  incurvated,  so  that  one  might  ride 
upon  its  back,  as  the  poets  imagined,  but  almost  straight.  When  it  is  first  taken  from 
the  water,  it  exhibits  a  variety  of  exquisitely  beautiful  but  evanescent  tints  of  color,  that 
pass  in  succession  over  its  body  until  it  dies.  They  are  an  extremely  swift-swimming 
fish,  and  are  capable  of  living  a  long  time  out  of  water ;  in  fact,  they  seem  to  delight  to 
gambol,  and  leap  out  of  their  native  element. 

"  Upon  the  swelling  waves  the  dolphins  show 
Their  bending  backs;  then  swiftly  darting  go, 
And  in  a  thousand  wreaths  their  bodies  show." 

TELESCOPIC  OBJECTS. 

1.  a,  DELPHINI — A  bright  star  with  a  distant  telescopic  companion;  R.  A.  20h.  82m. 
12s. ;  Dec.  N.  15*  21'  01'.    A  8%,  pale  white ;  B  13,  blue. 

2.  (3  DELPHINI— A  delicate  TRIPLE  STAR  on  the  Dolphin's  body,  1J$°  south-by-west  of  a, 
in  a  line  with  {3  Cygni  and  y  Lyra;  R.  A.  20h.  30m.  03s.;  Dec.  N.  14'  02'  06".    A  4, 
greenish  tinge ;  B  15,  and  C  12,  both  disky. 

8.  y  DELPHINI — A  beautiful  DOUBLE  STAR  in  the  head,  2°  east  of  a ;  R.  A.  20h.  89m. 
15s.:  Dec.  N.  15°  83'  02'.  A  4,  yellow;  B  7,  light  emerald,  with  a  third  star  about  2' 
distant. 

4.  A  delicate  QUADRUPLE  STAR,  near  e  in  the  tail ;  R.  A.  20h.  23m.  85s. ;  Dec.  N.  10"  48' 
06*.     A  7M,  and  B  8,  both  white;  C  16,  blue  ;  D  9,  yellowish  ;  several  other  small  stars 
in  the  field.    Map  VIII.,  Fig.  17. 

5.  A  SMALL  BRIGHT  CLUSTER,  in  the  Dolphin's  tail,  S%°  south  of  e  ;  R.  A.  20h.  26m.  21s. ; 
Dec.  N.  6°  53'  02".    Just  east  of  a  9th  magnitude  star— a  coarse  telescopic  pair  at  a 
distance,  and  several  minute  stars  in  the  field. 

6.  A  small  PLANETARY  NEBULA,  betwen  the  pectoral  fin  and  the  arrow  head,  6*  north- 
northwest  of  a,  and  exactly  on  a  line  towards  Vega  Lyrae  ;  R.  A.  20b.  15m.  15s. ;  Dec.  N 
19°  35,  06".    It  is  in  a  coarse  cluster,  in  the  center  of  which  are  fou4  c^r«pi<y>™w  »tara. 

HISTORY.— Accounts  of  the  origin  of  Delphinus?  What  said  of  Hesiod?  Of  Taras? 
Of  the  natural  shape,  &c.  ? 

TKLESCOPIC  OBJECTS.— Alpha ?  Beta?  Gamma?  What  quadruple  star?  Point  out 
m  the  map.  What  cluster?  Nebula? 


124  ASTRONOMY. 


OYGNUS  (THE  SWAN).— MAP  Y. 

226.  This  remarkable  constellation  is  situated  in  the  Milky- 
Way,  directly  E.  of  Lyra,  and  nearly  on  the  same  meridian  with 
the  Dolphin.     It  is  represented  on  outspread  wings,  flying  down 
the  Milky-Way,  toward  the  southwest. 

The  principal  stars  which  mark  the  wings,  the  body  and  the 
bill  of  Cygnus,  are  so  arranged  as  to  form  a  large  and  regular 
Cross  ;  the  upright  piece  lying  along  the  Milky- Way  from  N.  E. 
to  S.  W.,  while  the  cross  piece,  representing  the  wings,  crosses 
the  other  at  right  angles,  from  S.  E.  to  N.  W. 

227.  Arided  or  Dene.b  Cygni,  in  the  body  of  the  Swan,  is  a 
itar  of  the  second  magnitude,  24°  E.  N.  E.  of  Lyra,  and  30° 
directly  N.  of  the  Dolphin.     It  is  the  most  brilliant  star  in  the 
constellation.     It  is  situated  at  the  upper  end  of  the  cross,  and 
comes  to  the  meridian  at  9  o'clock  on  the  16th  of  September. 

Sad'r  is  a  star  of  the  8d  magnitude,  6*  S.  W.  of  Deneb,  situated  exactly  in  the  cross, 
or  where  the  upright  piece  intersects  the  cross  piece,  and  is  about  20°  E.  of  Lyra. 

Delta,  the  principal  star  in  the  west  wing,  or  arm  of  the  cross,  is  situated  N.  W.  of 
Sad'r,  at  the  distance  of  little  more  than  8°,  and  is  of  the  3d  magnitude.  Beyond  Delta, 
toward  the  extremity  of  the  wing,  are  two  smaller  stars  about  5"  apart,  and  inclining  a 
little  obliquely  to  the  north  ;  the  last  of  which  reaches  nearly  to  the  first  coil  of  Draco. 
These  stars  mark  the  west  wing ;  the  east  wing  may  be  traced  by  means  of  stars  very 
similarly  situated. 

6-ienah  is  a  star  of  the  3d  magnitude,  in  the  east  wing,  just  as  far  east  of  Sad'r  in  the 
center  of  the  cross,  as  Delta  is  west  of  it.  This  row  of  three  equal  stars,  Delta,  Sad'r 
and  Gienah,  form  the  bar  of  the  cross,  and  are  equi-distant  from  each  other,  being  about 
8°  apart.  Beyond  Gienah  on  the  east,  at  the  distance  of  6°  or  7°,  there  are  two  other 
stars  of  the  3d  magnitude;  the  last  of  which  marks  the  extremity  of  the  eastern  wing. 

The  stars  in  the  neck  are  all  too  small  to  be  noticed.  There  is  one,  however,  in  the 
beak  of  the  Swan,  at  the  foot  of  the  cross,  called  Albireo,  which  is  of  the  3d  magnitude, 
and  can  be  seen  very  plainly.  It  is  about  16°  S.  W.  of  Sad'r,  and  about  the  same  dis- 
tance S.  E.  of  Lyra,  with  which  it  makes  nearly  a  right  angle. 

"  In  the  small  space  between  Sad'r  and  Albireo,"  says  Dr.  Herschel,  "  the  stars  in  the 
Milky-Way  seem  to  be  clustering  into  two  separate  divisions  ;  each  division  containing 
more  than  one  hundred  and  sixty-Jive  thousand  stars." 

Albireo  bears  northerly  from  Altair,  about  20*.  Immediately  south  and  southeast  of 
Albireo,  may  be  seen  the  Fox  and  GOOSE  ;  and  about  midway  between  Albireo  and  Altair, 
there  may  be  traced  a  line  of  four  or  five  minute  stars,  called  the  ARROW  ;  the  head  of 
which  is  on  the  S.  W.,  and  can  be  distinguished  by  means  of  two  stars  situated  close 
together. 

228.  According  to  the  British  catalogue,  this  constellation 
contains  eighty-one  stars,  including  one  of  the  1st  or  2d  magni- 
tude, six  of  the  3d,  and  twelve  of  the  4th.     The  author  of  the 
following  beautiful  lines  says  there  are  one  hundred  and  seven. 

"Thee,  silver  Swan,  who1,  silent,  can  o'erpass? 
A  hundred  with  seven  radiant  stars  compose 
Thy  graceful  form  :  amid  the  lucid  stream 

226.  Situation  of  Cygnus?  How  represented?  Figure  made  by  its  principal  stars? 
Its  position?  227.  Which  is  the  brightest  of  its  stars?  Describe  Sad'r,  Delta,  Gienah, 
Albireo.  Remark  of  Dr.  Herschel?  228.  Number  of  stars  in  Cygnus?  Variable 
stars  ?  What  are  they  supposed  to  indicate  ? 


CYGNUS.  125 

Of  the  fair  Milky- Way  distinguished :  one 

Adorns  the  second  order,  where  she  cuts 

The  waves  that  follow  in  her  utmost  track; 

This  never  hides  its  fire  throughout  the  night, 

And  of  the  rest,  the  more  conspicuous  mark 

Her  snowy  pinions  and  refulgent  neck." — JSudosia,  b.  ir. 

Astronomers  have  discovered  three  variable  stars  in  the  Swan.  CM,  situated  in  the 
neck,  between  Beta  and  Sad'r,  was  first  observed  to  vary  its  brightness  in  1686.  Its  peri- 
odical changes  of  light  are  now  ascertained  to  be  completed  in  405  days.  Sad'r  is  also 
changeable.  Its  greatest  luster  is  somewhat  less  than  that  of  a  stur  of  the  3d  magnitude, 
and  it  gradually  diminishes  till  it  reaches  that  of  the  6th.  Its  changes  are  far  from  being 
regular,  and,  from  present  observations,  they  do  not  seem  to  recur  till  after  a  period  of 
ten  years  or  more. 

A  third  variable  star  was  discovered  in  the  head  on  the  20th  of  June,  1670,  by  Anthelme. 
It  appeared  then  to  be  of  the  3d  magnitude,  but  was  so  far  diminished  in  the  following 
October,  as  to  be  scarcely  visible.  In  the  beginning  of  April,  1671,  it  was  again  seen,  and 
was  rather  brighter  than  at  first.  After  several  changes,  it  disappeared  in  March,  1672- 
and  has  not  been  observed  since. 

These  icmarkable  facts  seem  to  indicate,  that  there  is  a  brilliant  planetary  system  in 
this  constellation,  which,  in  some  of  its  revolutions,  becomes  visible  to  us. 

HISTORY. 

Mythologists  give  various  accounts  of  the  origin  of  this  constellation.  Some  suppose 
it  is  Orpheus,  the  celebrated  musician,  who,  on  being  murdered  by  the  cruel  priestess  of 
Bacchus,  was  changed  into  a  Swan,  and  placed  near  his  Harp  in  the  heavens.  Otherg 
suppose  it  is  the  swan  into  which  Jupiter  transformed  himself  when  he  deceived  Leda, 
wife  of  Tyndarus,  king  of  Sparta.  Some  affirm  that  it  was  Cycnus,  a  son  of  Neptune, 
who  was  so  completely  invulnerable  that  neither  the  javelins  nor  arrows,  nor  even  tho 
blows  of  Achilles,  in  furious  combat,  could  make  any  impression. 

"  Headlong  he  leaps  from  off  his  lofty  car, 
And  in  close  fight  on  foot  renews  the  war ; — 
But  on  his  flesh  nor  wound  nor  blood  is  seen, 
The  sword  itself  is  blunted  on  the  skin." 

But  when  Achilles  saw  that  his  darts  and  blows  had  no  effect  on  him,  he  Immediately 
threw  him  on  the  ground  and  smothered  him.  While  he  was  attempting  to  despoil  him 
of  his  armor,  he  was  suddenly  changed  into  a  swan. 

44  With  eager  haste  he  went  to  strip  the  dead ; 
The  vanished  body  from  his  arms  was  fled. 
His  sea-god  sire,  to  immortalize  his  fame, 
Had  turned  it  to  a  bird  that  bears  his  name." 

According  to  Ovid,  this  constellation  took  its  name  from  Cycnus,  a  relative  of  Phaeton, 
who  deeply  lamented  the  untimely  fate  of  that  youth,  and  the  melancholy  end  of  hia 
sinters,  who,  standing  around  his  tomb,  wept  themselves  into  poplars. 

"  Cycnus  beheld  the  nymphs  transformed,  allied 
To  their  dead  brother  on  the  mortal  side, 
In  friendship  and  affection  nearer  bound  ; 
He  left  the  cities,  and  the  realms  he  owned, 
Through  pathless  fields,  and  lonely  shores  to  range ; 
And  woods  made  thicker  by  the  sisters'  change : 
While  here,  within  the  dismal  gloom  alone, 
The  melancholy  monarch  made  his  moan  ; 
His  voice  was  lessened  as  he  tried  to  speak, 
And  issued  through  a  long-extended  neck: 
His  hair  transforms  to  down,  his  fingers  meet 
In  skinny  films,  and  shape  his  oary  feet ; 
From  both  his  sides  the  wings  and  feathers  break  : 
And  from  his  mouth  proceeds  a  blunted  beak ; 
All  Cycnus  now  into  a  swan  was  turned."—  Ovid's  Met.  h.  H. 

HISTOKT.— Various  accounts  ?  Story  of  Cycnus  and  Achilles  ?  Ovid's  account  t  Vlr- 
gilS  runarkj  respecting  the  Swan? 


126  ASTRONOMY. 

Virgil,  also,      the  10th  book  of  his  ^Eneid,  alludes  to  the  same  fable  :—  • 
u  For  Cycnus  loved  unhappy  Phaeton, 
And  sung  his  loss  in  poplar  groves  alone 
Beneath  the  sister  shades  to  soothe  his  grief; 
Heaven  heard  his  song,  and  hasten'd  his  relief 
And  changed  to  snowy  plumes  his  hoary  hair, 
And  wing'd  his  flight  to  sing  aloft  in  air." 

Of  all  the  feathered  race,  there  is  no  bird,  perhaps,  which  makes  so  beautiful  and 
majestic  an  appearance  as  the.swan.  Almost  every  poet  of  eminence  has  taken  notico 
of  it.  The  swan  has,  probably,  in  all  ages,  and  in  every  country  where  taste  and  ele- 
gance have  been  cultivated,  bean  considered  as  the  emblem  of  poetical  dignity,  purity, 
and  ease.  By  the  ancients  it  was  consecrated  to  Apollo  and  the  Muses  ;  they  also  enter- 
tained a  notion  that  this  bird  foretold  its  own  end,  and  sang  more  sweetly  at  the 
approach  of  death. 

She,  like  the  swan 


Expiring,  dies  in  melody."— 
"  So  on  the  silver  stream,  when  death  is  nigh, 
The  mournful  swan  sings  its  own  elegy."—  Ovid's  Tristia. 

TELESCOPIC    OBJECTS. 

1.  a  CYGNI  (Deneb)  —  A  bright  star  on  the  back  of  the  Swan,  with  a  telescopic  com- 
panion ;  R.  A.  20h.  35m.  57s.  ;  Dec.  N.  44°  42'  07".    A  1,  brilliant  white  ;  B  12}$,  pale  blue. 

2.  {3  CYGNI  (Albireo)—*.  bright  DOUBLE  STAB  on  the  bill  of  the  figure  ;  R.  A.  19h.  24m. 
16s.  ;  Dec.  N.  27°  37'  07".    About  13  V  south-southeast  of  Vega.     A  3,  topaz  yellow  ;  B  7, 
sapphire  blue  ;  the  colors  in  brilliant  contrast.    A  fine  object,  and  the  first  double  star 
ever  seen  by  the  present  editor. 

3.  6  CYGNI—  A  most  delicate  DOUBLB  STAR  in  the  middle  of  the  left  wing,  14*  west  of  a 
Cygni;  R.  A.  19h.  39m.  58s.;  Dec.  N.  44"  44'  06".    A  3J$,  pale  yellow;  B  9,  sea  green. 
Another  beautiful  object. 

4  C  CYGNI  —  A  star  with  a  distant  companion,  on  the  tip  of  the  right  wing  ;  R.  A.  21h. 
06m.  07s.;  Dec.  N.  29°  84'  05".  A  3,  pale  yellow;  B  10,  sky  blue;  the  field  rich  in 
small  stars. 

5.  "k  CYGNI  —  A  close  DOUBLE  STAR  in  the  right  or  lower  wing,  with  a  distant  companion  ; 
R.  A.  20h.  41m.  11s.  ;  Dec.  N.  85*  54'  03".    A  5,  B  10,  and  C  6,  all  bluish. 

6.  V  CYGNI—  A  beautiful  DOUBLE  STAR,  with  a  distant  companion,  on  the  very  tip  of  the 
right  wing;   R.  A.  21h.  86m.  59s.;  Dec.  N.  28°  01'  04".    A  5,  white;   B  6,  and  0  TJ6, 
both  blue. 

7.  A  BINARY  STAR  (61  Cygni)—  the  most  remarkable  known  in  the  heavens.    It  is  situ- 
ated on  the  inner  tip  of  the  right  wing  of  Cygni,  7%°  south-by-east  of  Deneb,  and  nearly 
east  of  Vega  ;  R.  A.  20h.  59m.  43s.  ;  Dec.  N.  37°  58'  0".    A  52$,  and  B  6,  both  yellow,  but 
the  latter  of  the  deepest  tint.    From  the  great  rapidity  of  its  proper  motion,  this  star  13 
regarded  as  one  of  the  nearest  to  our  system.    It  affords  a  positive  instance  of  a  double 
star  which,  besides  the  individuals  revoiving  round  each  other,  or  about  their  common 
center  of  gravity,  has  a  progressive  uniform  motion  towards  some  determinate  region.   It  ia 
supposed  to  be  not  less  than  412,000  times  the  diameter  of  the  earth's  orbit  from  us  ;  or 
88,190,000,000,000  miles  distant  ;,  and  to  be  moving  through  space  60,000  times  as  fast  as 
Mercury  —  the  swiftest  body  known  to  our  system.    The  period  of  61  Cygni  as  a  binary 
system,  is  about  450  years.    For  orbit,  &c.,  see  Map  VIII.,  Fig.  18,  and  19. 

8.  A  fine  DOUBLB  STAR  on  the  tip  of  the  left  wing,  10°  northwest  of  a  Cygni,  and  within 
1*  of  0;  R.  A.  I9h.  87m.  84s.  ;  Dec.  N.  50°  09'  8".    A  6%  and  B  7,  both  pale  fawn  color. 

9.  A  WIDE  QUADRUPLE  STAR  in  a  rich  field,  on  the  Swan's  left  thigh,  about  8*  west  by 
north  of  Deneb  ;  R.  A.  20h.  08m.  86s.  ;  Dec.  N.  46*  15'  6'.   A  4,  orange  ;  B  16,  livid  ;  C  7%, 
and  D  53$,  both  cerulean  blue.    Not  the  effect  of  contrast. 

10.  A  NEAT  SMALL  CLUSTER  in  the  root  of  the  neck,  about  2°  south  of  y;  R.  A.  20h.  18m. 
17s.  ;  Dec.  N.  37°  59'  9".    A  8,  yellow;  B  11,  dusky. 

11.  A  LOOSE  SPLASHY  CLUSTER  in  a  rich  vicinity,  between  the  Swan's  tail  and  the  Lizard, 
due  south  of  (3  Cephei,  and  east-northeast  of  Deneb  ;  R.  A.  21h.  26m.  29s.  ;  Dec.  N.  47' 
48'  8". 


TELESCOPIC  OBJECTS.— Alpha?  Beta?  Delta?  Zeta?  Lambda?  Mu?  What  cele- 
brated binary  star?  Remarks  respecting?  Period?  Point  out  on  the  map.  What 
other  double  star  ?  Quadruple?  What  clusters ?  Nebula? 


CAPRICORNUS.  127 

12.  A  riRT  SIWGUIAR  NEBULA  on  the  tip  of  the  northern  wing,  about  5j£*  north  of 
<? ;  R.  A.  19h.  40m.  35s. ;  Dec.  N.  50"  07'  6*.  Seen  to  be  nebulous  only  with  good  instru- 
ments. Several  telescopic  stars  in  the  field.  The  Herschels  considered  this  aa  a  con 
necting  link  between  planetary  nebula  and  nebulous  stars. 


CAPEICORNUS  (THE  GOAT).-MAP  V. 

229.  This  is  the  tenth  sign,  and  eleventh  constellation,  in  the 
order  of  the  Zodiac,  and  is  situated  south  of  the  Dolphin,  and 
next  east  of  Sagittarius.     Its  mean  declination  is  20°  south,  and 
its  mean  right  ascension  310°.     It  is  therefore  on  the  meridian 
about  the  18th  of  September.     It  is  to  be  observed  that  the 
first  point  of  tbe  sign  Capricorn,  not  the  constellation,  marks  the 
southern  tropic,  or  winter  solstice.     The  sun,  therefore,  arrives 
at  this  point  of  its  orbit  the  21st  of  December,  but  does  not 
reach  the  constellation  Capricorn  until  the  16th  of  January. 

The  sun,  having  now  attained  its  utmost  declination  south,  after  remaining  a  few  days 
apparently  stationary,  begins  once  more  to  retrace  its  progress  northwardly,  affording  to 
the  wintry  latitudes  of  the  north  a  grateful  presage  of  returning  spring. 

At  the  period  of  the  winter  solstice,  the  sun  is  vertical  to  the  tropic  of  Capricorn,  and 
the  southern  hemisphere  enjoys  the  same  light  and  he?t  which  the  northern  hemisphere 
enjoys  on  the  21st  of  June,  when  the  sun  is  vertical  to  the  tropic  of  Cancer.  It  is,  at 
this  period,  mid-day  at  the  south  pole,  and  midnight  at  the  north  pole. 

230.  The  whole  number  of  stars  in  this  constellation  is  fifty- 
one  ;  none  of  which  are  very  conspicuous.     The  three  largest 
are  only  of  the  3d  magnitude.     There  is  an  equal  number  of 
the  4th. 

The  head  of  Capricorn  may  be  recognized  by  means  of  two 
stars  of  the  3d  magnitude,  situated  a  little  more  than  2°  apart, 
called  Giedi  and  Dalih.  They  are  28°  from  the  Dolphin,  in  a 
southerly  direction. 

Giedi  is  the  most  northern  star  of  the  two,  and  is  double.  Tf  a  line  be  drawn  from 
Lyra  through  Altair,  and  produced  about  23°  farther,  it  will  point  out  the  head  of  Capri- 
corn. These  two  stars  come  to  the  meridian  the  9th  of  September,  a  few  minutes  after 
Sad'r,  in  Cygnus.  A  few  other  stars  of  inferior  note  may  be  traced  out  by  reference  to 
the  maps. 

The  sign  of  the  Goat  was  called  by  the  ancient  orientalists  the  "  Southern  gate  of  the 
Sun,"  as  Cancer  was  denominated  the  "Northern  gate."  The  ten  stars  in  the  sign 
Capricorn,  known  to  the  ancients  by  the  name  of  the  "  Tower  of  Gad,"  are  probably  now 
in  the  constellation  Aquarius. 

HISTORY. 

Capricornus  is  said  to  be  Pan,  or  Bacchus,  who,  with  some  other  deities,  were  feasting 
near  the  banks  of  the  Nile,  when  suddenly  the  dreadful  giant  Tyjihon  came  upon  them, 
and  compelled  them  all  to  assume  a  different  shape,  in  order  to  escape  his  fury.  Ovid 
relates, 

"  How  Typhon,  from  the  conquer'd  skies,  pursued 
Their  routed  godheads  to  the  seven-mouth'd  flood  : 

229.  Position  of  Capricornus?  When  does  the  sun  enter  it?  What  said  of  his  place 
and  motion  at  that  time?  Of  the  winter  solstice?  230.  Number  of  stars  in  Capri- 
corn? Their  magnitudes?  How  recognize  the  figure ?  What  said  of  Giedi?  Ancient 
name  of  this  sign  ? 


128  ASTRONOMY. 

Forced  every  god  (his  fury  to  escape), 

Some  beastly  form  to  take,  or  earthly  shape. 

Jove  (sings  the  bard)  was  changed  into  a  ram, 

From  whence  the  horns  of  Libyan  Amnon  came; 

Bacchus  a  goat ;  Apollo  was  a  crow ; 

Phoebe  a  cat ;  the  wife  of  Jove  a  cow, 

Whose  hue  was  whiter  than  the  falling  snow; 

Mercury  to  a  nasty  ibis  turned — 

While  Venus  from  a  fish  protection  craves, 

And  once  more  plunges  in  her  native  waves." 

On  this  occasion  it  is  further  related  that  Bacchus,  or  Pan,  led  the  way  and  plunged 
into  the  Nile,  and  that  the  part  of  his  body  which  was  under  the  water  assumed  the  form 
of  a  fish,  and  the  other  part  that  of  a  goat ;  and  that  to  preserve  the  memory  of  this 
frolic,  Jupiter  made  him  into  a  constellation,  in  his  metamorphosed  shape. 

Some  say  that  this  constellation  was  the  goat  Amalthea,  who  supported  the  infan 
Jupiter  with  her  milk.  To  reward  her  kindness,  the  father  of  the  gods  placed  her  amonaf 
the  constellations,  and  gave  one  of  her  horns  to  the  nymphs  who  had  taken  care  of  him 
in  his  infantile  years.  This  gift  was  ever  after  called  the  horn  of  plenty;  as  it  possessed 
the  virtue  of  imparting  to  the  holder  whatever  she  desired.  On  this  account  the  Latin 
term  Cornucopia,  denotes  plenty,  or  abundance  of  good  things.  The  word  Amalthea, 
when  used  figuratively,  has  also  the  same  meaning. 

The  real  sense  of  tnis  fable,  divested  of  poetical  embellishment,  appears  to  be  this ; 
that  in  Crete,  some  say  in  Libya,  there  was  a  small  territory  shaped  very  much  like  ?». 
bullock's  horn,  and  exceedingly  fertile,  which  the  king  presented  to  his  daughter  Amal- 
thea, whom  the  poets  feigned  to  have  been  Jupiter's  nurse. 

"  The  bounteous  Pan,"  as  he  is  styled  by  Milton,  was  the  god  of  rural  scenery,  shep- 
herds, and  huntsmen.  Virgil  thus  addresses  him  :— 

"And  thou,  the  shepherd's  tutelary  god, 
Leave,  for  a  while,  0  Pan  !  thy  loved  abode." 

The  name  of  Pan  is  derived  from  a  Greek  word  signifying  aK  things;  and  he  was  oftea 
considered  as  the  great  principle  of  vegetable  and  ani-nal  life.  He  resided  chiefly  in 
Arcadia,  in  woods  and  the  most  rugged  mountains.  As  Pan  usually  terrified  the  inhabi- 
tants of  the  adjacent  country,  even  when  he  was  nowhere  to  be  seen,  that  kind  of  fear 
which  often  seizes  men,  and  which  is  only  ideal  or  imaginary,  has  received  from  him  the 
name  of  Panic. 

Pales,  the  female  deity  corresponding  to  Pan,  was  the  goddess  of  sheepfolds  and  of 
pastures  among  the  Romans.  Thus  Virgil : — 

"  Now,  sacred  Pales,  in  a  lofty  strain, 
1  sing  the  rural  honors  of  thy  reigu  ' 

The  shepherds  offered  to  this  goddess  milk  and  honey,  to  gain  her  protection  over  their 
flocks.  She  is  represented  as  an  old  woman,  and  was  worshiped  with  great  solemnity 
at  Rome.  Her  festivals,  which  were  called  Pulilia,  were  celebrated  on  the  20th  of  April, 
the  day  on  which  Romulus  laid  the  foundations  of  the  city. 

TELESCOPIC  OBJECTS. 

1.  a  CAPRICORNI — A  QUINTCPLE  STAR  in  the  right  horn  ;  R.  A.  20h.  09m.  10s. ;  Dec.  S.  13* 
02'  1".    A  3,  pale  yellow;  B  (or  a  1)  4,  yellow  ;  C  16,  blue;  D  9,  ash-colored;  E  91$,  lilac 
tinge.     Few  telescopes  will  reveal  all  these  components. 

2.  j3  CAPRICORNI — A  wide   PAIR  OF  STARS  in  the  right  horn,  2%"  south-half-east  of  a; 
R.  A.  20h.  12m.  Ols. ;  Dec.  S.  15°  16'  9".    A  3^,  orange  yellow;  B  7,  sky  blue.     Other 
small  stars  in  the  field.    It  requires,  a  powerful  instrument,  and  the  most  favorable  cir- 
cumstances to  detect  the  minute  star  5.     (See  Map  VIII.,  Fig.  20.) 

3.  A  GLOBULAR  CLUSTER  between  Aquarius  and  the  neck  of  Capricorn,  9°  due  east  of 
a  Capricorni,  about  j£°  from  a  6th  magnitude  star;  R.  A.  20h.  44m.  89s. ;  Dec.  S.  13"  07' 
6".    Many  stars  in  the  field,  two  of  which  are  close  to  the  cluster,  or  the  east.  Map  IX., 
Fig.  63. 

HISTORY. — Who  was  Capricornus  ?  What  proof  cited?  What  further?  What  other 
myth  ?  Meaning  of  this  fable  ?  What  said  of  Pales  ? 

TELESCOPIC  OBJECTS.— Alpha?  Beta?  Point  out  on  the  map ?  What  clusters?  Where 
nhown  on  the  map  ? 


PEGASUS  12(J 

4.  A  fine  PALB  WHITK  CLUSTER,  about  20*  west-northwest  of  Fomalh\ut;  R.  A.  21!^ 
lira.  16s. ;  Dec.  S.  23*  68'  4"-  A  bright  object,  with  straggling  streams  of  stars,  and  but 
few  outliers  in  the  field.  Seen  with  small  instruments.  Map  IX.,  Fig.  64. 


CHAPTER  XII. 

CONSTELLATIONS      ON     THE      MERIDIAN     IN     OCTOBER. 

PEGASUS  (THE  FLYING  HOESE). — MAP  II. 

231.  THIS  constellation  is  represented  in  an  inverted  posture, 
with  wings.     It  occupies  a  large  space  in  the  heavens,  between 
the  Swan,  the  Dolphin  and  the  Eagle,  on  the  west,  and  the  Nor- 
thern Fish  and  Andromeda,  on  the  east.     Its  mean  right  ascen- 
sion is  340°,  or  it  is  situated  20°  W.  of  the  prime  meridian.     It 
extends  from  the  equinoctial  N.  35°.     Its  mean  length  E.  and 
W.  is  about  40°,  and  it  is  six  weeks  in  passing  our  meridian, 
viz.,  from  the  1st  of  October  to  the  10th  of  November. 

232.  We  see  but  a  part  of  Pegasus,  the  rest  of  the  animal 
being,  as  -the  poets  imagined,  hid  in  the  clouds.     It  is  readily 
distinguished   from  all   other   constellations   by  means  of  four 
remarkable  stars,  about  15°  apart,  forming  the  figure  of  a  square 
called  the  Square  of  Pegasus. 

The  two  western  stars  in  this  square  come  to  the  meridian  about  the  23d  of  October, 
and  are  13°  apart.  The  northern  one,  which  is  the  brightest  of  three  triangular  stars 
in  the  martingale,  is  of  the  2d  magnitude,  and  is  called  Scheat.  Its  declination  is 26%°. 
Markab,  also,  of  the  2d  magnitude,  situated  in  the  head  of  the  wing,  is  13"  S.  of  Scheat, 
and  passes  the  meridian  11  minutes  after  it. 

The  two  stars  which  form  the  eastern  side  of  the  square,  come  to  the  meridian  about 
an  hour  after  those  in  the  western.  The  northern  one  has  already  been  described  as 
Alpheratz  in  the  head  of  Andromeda,  but  it  also  belongs  to  this  constellation,  and  is  14' 
E.  Scheat.  14*  S.  of  Alpheratz,  is  Algenib,  the  last  star  in  the  wing.situated  16V  E.  of 
Markab. 

233.  Algenib  in  Pegasus,  Alpheratz  in  Andromeda,  and  Caph 
in  Cassiopeia  are  situated  on  the  prime  meridian,  and  point  out 
its  direction  through  the  pole.     For  this  reason  they  are  some- 
times called  the  three,  guides.     They  form  an  arc  of  that  great 
circle  in  the  heavens  from  which  the  distances  of  all  the  heavenly 
bodies  are  measured. 

231.  What  constellations  in  this  chapter?  Describe  Pegasus,  its  size,  position,  &c. 
232.  Do  we  see  the  whole  of  the  figure  ?  How  is  it  distinguished?  What  said  of  Scheat 
and  Markab?  Of  Alpheratz  and  Algenib?  233.  Remark  respecting  Algenib,  Alphe- 
ratz and  Caph?  What  sometimes  called,  and  why?  They  form  what?  Rem»rke 


130  ASTRONOMY. 

It  is  an  arc  of -the  equinoctial  ;olure  which  passes  through  the  vernal  equinox,  n.ad 
which  the  sun  crosses  about  the  2 1st  of  March.  It  is,  in  astronomy,  what  the  meridian 
of  Greenwich  is  in  geography.  If  the  sun,  or  a  planet,  or  a  star,'  be  said  to  have  so  many 
degrees  of  right  ascension,  it  means  that  the  sun  or  planet  has  ascended  so  many  degiees 
from  this  prime  meridian. 

Enif,  sometimes  called  Enir,  is  a  star  of  the  3d  magnitude  in  the  nose  of  Pegaaus, 
nbout  20*  W.  S.  W.  of  Markab,  and  half-way  between  it  and  the  Dolphin.  About  half  of 
the  distance  from  Markab  toward  Enif,  but  a  little  to  the  S.,  there  is  a  star  of  the  8d  mag- 
nitude situated  in  the  neck,  whose  letter  name  is  Zeta.  The  loose  cluster  directly  S.  c« 
the  line  joining  Enif  and  Zeta,  forms  the  head  of  Pegasus. 

In  this  constellation  there  are  eighty-nine  stars  visible  to  the  naked  eye,  of  which  tL/ee 
are  of  the  second  magnitude  and  three  of  the  third. 

HISTORY. 

This,  according  to  fable,  is  the  celebrated  horse  which  sprung  from  the  blood  of  Medusa, 
after  Perseus  had  cut  off  her  head.  He  received  his  name  according  to  Hesiod,  from  hig 
being  born  near  the  sources  (TTTJ'/IJ,  Pege)  of  the  ocean.  According  to  Ovid,  he  fixed  his 
residence  on  Mount  Helicon,  where,  by  striking  the  earth  with  his  foot,  he  raised  the 
fabled  fountain  called  Hippocrene.  He  became  the  favorite  of  the  Muses ;  and  being 
tamed  by  Neptune  or  Minerva,  he  was  given  to  Bellerophon,  son  of  Glaucus,  king  of 
Ephyre,  to  aid  him  in  conquering  the  Chimsera,  a  hideous  monster  that  continually  vom- 
ited flames.  This  monster  had  three  heads,  that  of  a  lion,  a  goat,  and  a  dragon.  The 
fore  parts  of  its  body  were  those  of  a  lion,  the  middle  those  of  a  goat,  and  the  hin  ler 
those  of  the  dragon.  It  lived  in  Lycia,  of  which  the  top,  on  account  of  its  desolate  wil- 
derness, was  the  resort  of  lions,  the  middle,  which  was  fruitful,  was  covered  with  goats, 
and  at  the  bottom,  the  marshy  ground  abounded  with  serpents.  Bellerophon  was  the 
first  who  made  his  habitation  upon  it. 

Plutarch  thinks  the  Chimaera  was  the  captain  of  some  pirate  who  adorned  their  ship 
with  the  images  of  a  lion,  a  goat,  and  a  dragon. 

After  the  destruction  of  this  monster,  Bellerophon  attempted  to  fly  up  to  heaven  upon 
Pegasus ;  but  Jupiter  was  so  displeased  at  this  presumption,  that  he  sent  an  insect  to 
sting  the  horse,  which  occasioned  the  melancholy  fall  of  his  rider.  Bellerophon  fell  to 
the  earth,  and  Pegasus  continued  his  flight  up  to  heaven,  and  was  placed  by  Jupiter 
among  the  constellations. 

"  Now  heav'n  his  further  wand'ring  flight  confines, 
Where,  splendid  with  his  num'rous  stars,  he  shines." 

OvWs  fasti. 

TELESCOPIC  OBJECTS, 

1.  a  PEGASI  (Markab) — A  star  with  a  distant  companion,  at  the  junction  of  the  wing 
and  shoulder,  13"  south  of  Scheat ;  R.  A.  22h.  56m.  47s. ;  Dec.  N.  14*  20'  08".    A  2,  white  ; 
B  11,  pale  grey. 

2.  /3  PEQASI  (Sclieaf) — A  bright  star  with  a  minute  distant  companion,  on  the  left  fore- 
leg; R.  A.  22h.  56m.  Ols. ;   Dec.  N.  27°  13'  0".    A  2,  deep  yellow  ;   B  15,  blue  ;  with  two 
other  stars  in  the  field. 

8.  y  PEGASI  (Algenib) — A  star  with  a  distant  companion,  on  the  edge  of  the  wing; 
R.  A.  Oh.  05m.  Os. ;  Dec.  N.  14"  17'  07".  A  2%,  yellow ;  B  13,  pale  blue. 

4.  e  PEGASI  (Enif) — A  star  with  two  distant  companions,  in  the  nose  of  the  figure ; 
R.  A.  21h.  36m.  19s. ;  Dec.  N.  9°  08'  07".    A  2%,  yellow ;  B  14,  blue  ;  C  9,  violet;  and  a 
9th  magnitude  star  of  a  viokt  tinge,  at  a  distance  east. 

5.  (,  PKGASI — A  star  with  a  minute  companion  in  the  middle  of  the  neck ;  R.  A.  22h.  o<im- 
29s. ;  Dec.  N.  9°  59'  9".     A  line  from  Alpheratz  over  Markab,  and  carried  7°  further,  will 
reach  f.     A3,  light  yellow;  B  13,  dusky;  with  other  stars  in  the  field. 

6.  A  DOUBLE  STAR  between  the  head  of  Pegasus  and  the  hind  legs  of  the  Fox ;  or  about 
10  j£*  south  by  east  of  f  Cygni;  R.  A.  21h.  14m.  41s. ;  Dec.  N.  19°  07'  4".  A  4,  pale  orange, 
and  considered  variable ;  B  9,  purplish. 

respecting  the  prime  meridian  ?    What  said  of  Enif?    Of  Zeta  ?    Of  the  head  of  Pegasus 
Number  of  stars  in  the  constellation,  and  their  magnitudes? 

HISTORY. — Story  of  his  origin  and  name  ?  Residence,  <fec.  ?  How  he  came  among  tho 
•tars  ? 

TKLIMCOPIC  OBJECTS.— Alpha?  Beta?  Gamma?  Epsilon?  Zeta?  What  double  starr 
What  cluster  ?  Point  out  on  the  map.  What  nebula  ? 


AQUARIUS.  131 

7.  A  GLOBULAR  CLUSTKR  between  the  mouths  of  Pegasus  and  Eqiileus,  about  4*  north- 
west  of  e;  R.  A.  21h.  22m.  18s. ;  Dec.  N.  11°  27'  4".     Map  IX.,  Fig.  65.    It  is  laid  down  aa 
l  nebula  on  Map  II.,  but  with  a  good  instrument  it  is  resolved  into  stars,  with  straggling 
outliers,  as  shown  in  the  diagram. 

8.  An  ELONGATED  NEBULA  in  the  animal's  mane,  about  3"  due  south  of  Markab ;  R.  A. 
22h.  56m.  58s. ;  Dec.  N.  11"  27'  9'.    A  very  faint  and  difficult  object. 


EQULEUS,   YEL   EQUI    SECTIO    (THE    LITTLE    HOBSE,   OR   THE 
HORSE'S    HEAD). — MAP    II. 

234.  This  Asterism,  or  small  cluster  of  stars,  is  situated  about 
1°  W.  of  Enif,  in  the  head  of  Pegasus,  and  about  half-way 
between  it  and  the  Dolphin.  It  is  on  the  meridian  at  8  o'clock, 
on  the  llth  of  October.  It  contains  ten  stars,  of  which  the 
four  principal  are  only  of  the  4th  magnitude.  These  may  be 
readily  distinguished  by  means  of  the  long  irregular  square 
which  they  form.  The  two  in  the  nose  are  much  nearer  together 
than  the  two  in  the  eyes  :  the  former  being  1°  apart,  and  the 
latter  2-j-0.  Those  in  the  nose  are  uppermost,  being  4°  N.  of 
those  in  the  eyes.  This  figure  also  is  in  an  inverted  position. 
These  four  stars  are  situated  10°  or  12°  S.  E.  of  the  diamond 
in  the  Dolphin's  head.  Both  of  these  clusters  are  noticeable  on 
account  of  their  figure  rather  than  their  brilliancy. 

HISTORY. 

This  constellation  is  supposed  to  be  the  brother  of  Pegasus,  named  Celeris,  given  by  Mer- 
cury to  Castor,  who  was  so  celebrated  for  his  skill  in  the  management  of  horses ;  others* 
take  him  to  be  the  celebrated  horse  which  Neptune  struck  out  of  the  earth  with  his  tri- 
dent, when  he  disputed  with  Minerva  for  superiority.  The  head  only  of  Celeris  is 
visible,  and  this,  also,  is  represented  in  an  inverted  position. 

TELESCOPIC  OBJECTS. 

Four  of  the  principal  stars  in  this  little  group  are  double — namely,  /?,  (J,  £  and  A.  /3 
is  rather  a  star  with  a  companion ;  R.  A.  21h/  14m.  57s. ;  Dec.  N.  6*  07'  8".  The  other 
three  will  easily  be  found  from  their  proximity  to  8. 


AQUAEIUS  (THE  WATER-BEARER).— MAP  II. 

235.  This   constellation   is    represented  by  the   figure  of  a 
pouring  out  water  from  an  urn.     It  is  situated  in  the  Zodiac, 
immediately  S.  of  the  equinoctial,  and  bounded  by  the  Little 

234.  Situation  of  Eqiileus  ?     When  on  the  meridian  ?    Number  of  stars,  and  how  dJs- 
linguished?    What  further  description  ? 

HISTORY. — What  suppositions  respecting  the  origin  of  Eqiileus  ? 
TKI.KSCOPIC  OBJECTS. — What  double  stars?    How  found"? 
'i85.  How  ia  Aquarius  represented  ?    Its  boundaries  ? 

6* 


132  ASTRONOMY. 

Horse,  Pegasus,  and  the  Western  Fish  on  the  N.f  the  Whale  O'l 
the  E.,  the  Southern  Fish  on  the  S.  and  the  Goat  on  the  W. 

236.  Aquarius   is   now  the    12th  in  order,   or  last    of   the 
Zodiacal  constellations  ;  and  is  the  name  of  the  llth  sign  in  the 
ecliptic.      Its  mean   declination   is  14°  S.,  and  its  mean  right 
ascension  335°,  or  22  hours,  20  min.  ;  it  being  1  hour  and  40 
min.  W.  of  the  equinoctial  colure  ;  its  center  is,  therefore,  on 
the  meridian  the  15th  of  October. 

It  contains  one  hundred  and  eight  stars  ;  of  which  the  four 
largest  are  all  of  the  3d  magnitude. 

"  His  head,  his  shoulders,  and  his  lucid  breast, 
Glisten  with  stars  ;  and  where  his  urn  inclines, 
Rivers  of  light  brighten  the  watery  track." 

237.  The  northeastern  limit  of  Aquarius  may  be  readily  dis- 
tinguished by  means  of  four  stars  of  the  4th  magnitude,  in  the 
hand  and  handle  of  the  urn,  so  placed  as  to  form  the  letter  Y, 
very  plainly  to  be  seen,  15°  S.  E.  of  JEnif,  or  18°  S.  S.  W.  of 
Markab,  in  Pegasus  ;  making  with  the  two  latter  nearly  a  right 
angle. 

About  4J£*  W.  of  the  figure  is  El  Melik,  a  star  of  the  3d  magnitude,  in  the  E.  shoulder, 
and  the  principal  one  in  this  constellation.  10°  S.  W.  of  El  Melik,  is  another  star  of  the 
Bame  magnitude,  situated  in  the  W.  shoulder,  called  Sad  es  Saud. 

Ancha,  of  the  4th  magnitude,  is  in  the  right  side,  8*  S.  of  El  Melik.  9*  E.  of  Ancha,  is 
another  star  of  the  4th  magnitude,  whose  letter  name  is  Lambda. 

iScheat,  of  the  3d  magnitude,  lying  below  the  knee,  is  situated  8j£*  S.  of  Lambda;  and 
14°  S.  of  Scheat,  the  brilliant  star  Fomalhaut,  of  between  the  1st  and  2d  magnitudes,  ter- 
minates the  cascade  in  the  mouth  of  the  Southern  Pish.  This  star  is  common  to  both 
these  constellations,  and  is  one  of  those  from  which  the  lunar  distance  is  computed  for 
ascertaining  the  longitude  at  sea.  It  culminates  at  9  o'clock  on  the  22d  of  October. 

Fomalhaut,  Deneh  Kaitos,  and  Alpha  in  the  head  of  the  Phosnix,  make  a  large  triangle, 
whose  vertex  is  in  Deneb  Kaitos.  Those  two  stars  of  the  fourth  magnitude,  situated  4* 
S.  of  Sad  es  Saud,  and  nearly  the  same  distance  from  Ancha,  are  in  the  tail  of  Capricorn. 
They  are  about  2°  apart.  The  western  one  is  called  Deneb  Algedi. 

The  rest  of  the  stars  in  the  cascade  are  quite  small ;  they  may  be  traced  from  the 
Letter  Y,  in  the  urn,  in  a  southeasterly  direction  toward  the  tail  of  Cetus,  from  which  the 
cascade  suddenly  bends  off  near  Scheat,  in  an  opposite  course,  and  finally  disappears  in 
the  mouth  of  the  Southern  Fish,  30°  S.  of  Y. 

HISTORY. 

This  constellation  is  the  famous  Ganymede,  a  beautiful  youth  of  Phrygia,  son  of  Tros, 
king  of  Troy,  or,  'according  to  Lucian,  son  of  Dardanus.  He  was  taken  up  to  heaven  by 
Jupiter  as  he  was  tending  his  father's  flocks  on  Mount  Ida,  and  became  the  cup-bearer 
of  the  gods  in  place  of  Hebe.  There  are  various  opinions,  however,  among  the  ancients 
respecting  its  origin.  Some  suppose  it  represents  Deucalion,  who  was  placed  among  the 
stars  after  the  celebrated  deluge  of  Thessaly,  1500  years  before  the  birth  of  our  Saviour  ; 
while  others  think  it  designed  to  commemorate  Cecrops,  who  came  from  Egypt  to  Greece, 
founded  Athens,  established  science,  and  introduced  the  arts  of  polished  life. 

The  ancient  Egyptians  supposed  the  setting  or  disappearance  of  Aquarius  caused  the 
Nile  to  rise,  by  the  sinking  of  his  urn  in  the  water.  In  the  Zodiac  of  the  Hebrews, 
Aquarius  represents  the  tribe  of  Reuben. 

ts  order  in  the  signs  and  constellations  ?  Number  and  size  of  its  stars  ?  237.  How 
distinguish  the  northeast  limit?  What  said  of  El  Melik?  Of  Sad  es  Saud?  Of  Ancha., 
Lambda,  Scheat,  &c. 

HISTORY.— Story  of  Ganymede,  and  Jupiter?  What  other  myth?  Idea  of  the  EKVP 
tain*?  Hebrew  Zodiac  ? 


PISCES    ATJSTRALIS. 


TELESCOPIC  OBJECTS. 

1.  a  AV"ARII  (PharcT) — A  star  with  a  minute  companion  on  the  Water-bearer's  left, 
ahoulder;  R  A.  21h.  57m.  33s.;   Dec.  S.  1°  05'  07*.    A  3,  pale  yellow;  B  13,  grey;  and 
another  star  in  the  field  on  a  line  with  A  and  B.    Afarkab  is  on  a  line  joining  Alpheratz 
nnd  Phard,  and  about  half  way  between  them. 

2.  0  AQUARII  (Sad-al-melik)—^  star  with  a  companion  on  the  right  shoulder ;  R.  A. 
21h.  23m.  07s. ;  Dec.  N.  6°  16'  04'.    A  3,  pale  yellow ;  B  15,  blue.    A  very  delicate  object. 

3.  7  AQUARII— A  delicate  but  wide  DOUBLE  STAR,  on  the  water-pot;  R.  A.  22h.  13m. 
'23s. ;  Dec.  S.  2"  11'  05".    A  4,  greenish  tinge ;  B  14,  purple.    It  is  about  4°  east-by-south 
from  Sad-al-melik. 

4.  f  AQUARII — A  BINARY  STAR  in  the  left  wrist,  about  6°  east  from  Sadalmelik ;  R.  A. 
22h.  20m.  35s. ;  Dec.  S.  0*  50'  02'.    A  4,  very  white ;  B  4^,  white. 

f>.  T'  AQUARII — A  fine  DOUBLE  STAR  in  the  left  leg,  one  third  of  the  way  from  Fomalhaut 
to  £ Pegasi ;  R.  A.  22h.  39m.  13s. ;  Dec.  S.  14"  53'  09".  A  6,  white ;  B  9J$,  pale  garnet. 

6.  i/>'  AQUARII — A  DOUBLE  STAR  in  the  stream,  being  the  first  of  three  similar  stars 
marked  ^1,  ^a,  i/,3 ;  R.  A.  23h.  07m.  80s. ;  Dec.  S.  9°  57'  05".  A  5%,  orange  tint ;  B  9,  sky 
blue.  It  is  about  one-third  of  the  way  from  Fomalhaut  to  a  Andromedse.  Several  other 
beautiful  double  stars  east  of  Scheat,  in  the  stream,  as  shown  on  the  map. 

T.  A  FINK  GLOBULAR  CLUSTER  near  the  neck  of  Aquarius,  about  5°  north-half-east  from 
/9;  R.  A.  2th.  23m.  07s. ;  Dec.  S.  6°  16'  04".  A  cluster  of  exceedingly  small  stars,  which 
has  been  likened  to  "  a  heap  of  fine  sand."  Several  telescopic  outliers  in  the  field.  Map 
VIII.,  Fig.  66. 

8.  A  PLANETARY  NEBULA  in  the  middle  of  the  scarf;  R.  A.  20h.  55m.  27s. ;  Dec.  S.  11' 
59'  08".  About  12°  east  of  a  Capricorni,  where  a  line  from  the  Eagle's  tail  over  6  Anti- 
noi,  and  as  far  again,  reaches  it.  It  is  bright  to  its  very  disc,  and  but  for  itapale  bluo 
tint,  would  be  a  very  miniature  of  Venus. 


PISCES  AUSTRALIS  (THE  SOUTHERN  FISH). — MAP  II. 

238.  This  constellation  is  directly  S.  of  Aquarius,  and  is 
represented  as  a  fish  drinking  the  water  which  Aquarius  pours 
from  his  urn.  Its  mean  declination  is  31°  S.  and  its  mean  right 
ascension  and  time  of  passing  the  meridian  are  the  same  as  those 
of  .Aquarius,  and  it  is  seen  on  the  meridian  at  the  same  time, 
viz.  on  the  15th  of  October.  It  contains  24  visible  stars,  of 
which  one  is  of  the  1st  magnitude,  or  between  the  1st  and  2d,  two 
are  of  the  3d,  and  five  of  the  4th.  The  first  and  most  beautiful 
of  all  is  Fomalhaut,  situated  in  the  mouth.  This  is  14°  directly 
S.  of  Scheat  in  Aquarius,  and  may  be  seen  passing  the  meridian 
low  down  in  the  southern  hemisphere,  on  the  22d  and  23d  of 
October.  Its  position  in  the  heavens  has  been  determined  with 
the  greatest  possible  accuracy,  to  enable  navigators  to  find  their 
longitude  at  sea. 

The  mode  of  doing  this  cannot  be  explained  here.  The  proolen  is  one  of  some  difficulty. 
It  consists  in  finding  the  angular  distance  between  some  star  whose  position  is  well  known, 

TELESCOPIC  OBJECTS.— Alpha?  Beta?  Gamma?  Zeta?  Tau?  Psi?  What  clusters, 
and  where  shown  on  the  map  ?  What  nebula? 

233.  Situation  of  Pisces  Australia  ?  How  represented  ?  When  on  the  meridian  ?  Num- 
ber of  stars  ?  Magnitude  ?  The  principal  star  ?  How  situated  ?  What  use  made  of  it? 
What  said  of  the  method  of  finding  the  longitude  by  the  moon  and  stars? 


134.  ASTRONOMY. 

and  <Jie  moon  when  she  is  passing  near  it;  also,  the  altitude  of  each,  at  the  same  instant, 
with  good  sextants.  These  data  furnish  the  elements  of  a  spherical  triangle,  the  solution 
of  which,  after  various  intricate  corrections,  is  made  to  result  in  the  longitude  of  the  given 
place. — See  note  to  Arietes.  In  1714,  the  British  Parliament  offered  a  reward  of  10,000 
pounds  sterling,  to  any  man  who  should  discover  a  method  of  determining  the  longitude 
within  1°,  or  60  geographical  miles  of  the  truth ;  15,000  pounds  to  the  man  who  shou.ll 
find  it  within  40  miles,  and  20,000  pounds,  if  found  within  30  miles.  These  rewards  in  part, 
have  been  since  distributed  among  eminent  mathematicians,  in  Europe,  agreeably  to  the 
respective  merits  of  their  discoveries. 

HISTORY. 

This  constellation  is  supposed  to  have  taken  its  name  from  the  transformation  of  Venua 
into  the  shape  of  a  fish,  when  she  fled,  terrified  at  the  horrible  advances  of  the  monster 
Typhon,  as  we  have  related  in  the  mythology  of  the  Fishes. — (See  Pisces.) 

TELESCOPIC  OBJECTS. 

a  PISCES  AUSTRALIS— A  first  magnitude  star  with  a  very  distant  companion,  in  the  eye 
of  the  fish ;  R.  A.  22h.  48m.  48a. ;  Dec.  S.  80°  28'  03'.  A  1,  reddish ;  B  9  J<$,  dusky  blue. 


LACERTA  (THE  LIZAED).— MAP  II. 

239.  This  is  a  small  and  obscure  modern  constellation,  between 
the  tail  of  Cygnus  and  the  head  of  Andromeda.     It  has  one  star 
of  the  4th  magnitude,  eight  of  the  5th,  and  a  few  much  smaller. 

240.  Between   Lacerta   and  Andromeda  a  singular  looking 
figure  appears  on  the  map,  called  Gloria  Frederica;  or  Frederics 
Glory.     It  was  inserted  among  the  constellations  by  Bode,  in 
1787,  as  a  compliment  to  Frederic  II.,  of  Prussia.     It  consists 
of  a  crown,  a  laurel,  a  sword,  and  a  pen,  to  represent  the  mon- 
arch, the  hero,  the  sage,  and  the  pacificator.     But  the  constel- 
lation was  not  recognized  by  astronomers,   and,  as   such,  has 
already  passed  from  the  heavens. 

TELESCOPIC  OBJECTS. 

1.  A  neat  DOCBLH  STAR  on  the  tip  of  the  Lizard's  tail ;  R.  A.  22h.  llm.  56s. ;  Dec.  N. 
86°  58'  01'.    A  6J$,  pale  white  ;  B  9,  livid. 

2.  A  delicate  but  wide  DOUBLE  STAR  on  the  shoulder  ;  R.  A.  22h.  14m.  25s. ;  Dec.  N.  45* 
43'  09".    A  5,  pale  yellow;  B  13,  orange  tint.    A  line  from  Polaris  carried  by  the  east  of 
Cepheus  tiara,  and  11*  further,  will  find  it  the  lucida  of  a  fine  galaxy  field. 

8.  A  WIDE  DOUBLE  STAR  near  the  end  of  the  tail,  the  southern  star  of  three  forming  a 
neat  triangle  ;  R.  A.  22h.  82m.  05s. ;  Dec.  N.  38°  13'  2".  A  6%,  white ;  B  10,  violet. 

4.  A  DELICATI  TRIPLE  STAR  in  the  space  between  the  Lizard's  back  and  the  left  hand  of 
Andromeda;  R.  A.  22h.  49m.  06s.;  Dec.  N.  40°  45'  1".  A  6,  bright  white;  B.  15,  pale 
blue;  C  9J6,  reddish;  a  fourth  star  at  a  distance.  A  very  difficult  object;  claimed  by 
Home  for  Andromeda,  but  usually  classed  as  belonging  to  the  Lizard. 

HISTORY. — Supposed  origin  of  this  constellation  ? 

TELESCOPIC  OBJECTS. — Alpha?    Where  situated? 

239.  Describe  Lacerta.  Where  situated?  240.  Whatother  small  constellation  near P 
By  whom  inserted,  when  and  why?  Of  what  does  it  consist?  To  represent  what?  Is  it 
recognized  by  astronomers  ? 

TELESCOPIC  OBJECTS. — What  double  stars  in  Lacerta T  What  triple  star?  Quadruple? 
Cluster?  Any  of  them  shown  on  the  map? 


VARTABLE  AND  DOUBLE  STARS.  135 

5.  A  QUADRUPLE  STAR,  the  western  one  of  the  three  forming  the  triangle  at  the  end  of 
the  tail ;  R.  A.  22h.  29m.  46s. ;  Dec.  N.  88°  48'  5'.    About  20°  northwest  of  Alpheratz.    A 
and  B  6J^,  both  white  ;  C  11,  greenish ;  D  10,  blue. 

6.  A  LARGB  LOOSE  CLUSTER  in  th  ?  Lizard's  mouth  ;  R.  A.  v^h.  08m.  59s. ;  Dec.  N.  49'  05 
1*.    Stars  from  the  9th  to  the  14th  magnitudes.  -A  line  carried  from  Polaris  through  t'ut 
tiara  of  Cepheus,  and  8°  beyond,  strikes  it. 


CHAPTER    XIII. 

VARIABLE    AND    DOUBLE    STARS— CLUSTERS    AND 
NEBULAE. 

241.  THE  periodical  variations  of  brilliancy  to  which  some  of 
the  fixed  stars  are  subject,  may  be  reckoned  among  the  most 
remarkable  of  their  phenomena.     Several  stars,  formerly  distin- 
guished by  their  splendor,  have  entirely  disappeared  ;  others  are 
now  conspicuous  which  do  not  seem  to  have  been  visible  to  the 
ancient  observers  ;  and  there  are  some  which  alternately  appear 
and  disappear,  or,  at  least,  of  which  the  light  undergoes  great 
periodic    changes.      Some    seem   to   become    gradually  more 
obscure,  as  Delta  in  the  Great  Bear  ;  others,  like  Beta  in  the 
Whale,  to  be  increasing  in  brilliancy. 

242.  Some  stars  have  all  at  once  blazed  forth  with  great  splen- 
dor, and,  after  a  gradual  diminution  of  their  light,  again  become 
extinct.     The  most  remarkable  instance  of  this  kind  is  that  of 
the  star  which  appeared  in  1512,  in  the  time  of  Tycho  Brahe. 
It  suddenly  shone  forth  in  the  constellation  Cassiopeia,  with  a 
splendor  exceeding  that  of  stars  of  the  first  magnitude,  even  of 
Jupiter  and  of  Yenus,  at  their  least  distances  from  the  earth  ; 
and  could  be  seen  with  the  naked  eye,  on  the  meridian,  in  full 
day!     Its  brilliancy  gradually  diminished  from  the  time  of  its 
first  appearance,  and  at  the  end  of  sixteen  months  it  entirely 
disappeared,  and  has  never  been  seen  since.     (See  a  more  par- 
ticular account  of  this  phenomenon,  page  35.^) 

Another  instance  of  the  same  kind  was  observed  in  1604,  when  a  star  of  the  first  mag- 
nitude suddenly  appeared  in  the  right  foot  of  Ophiuchus.  It  presented,  like  the  former, 
all  the  phenomena  of  a  prodigious  flame,  being,  at  first,  of  a  dazzling  white,  then  of  a 
reddish  yellow,  and,  lastly,  of  a  leaden  paleness  ;  in  which  its  light  expired.  These 
instances  prove  that  the  stars  are  subject  to  great  physical  revolutions.  (Puge  ()0) 

243.  A  great  number  of  stars  have  been  observed  whose  lip-^it 
seems  to  undergo  a  regular  periodic  increase  and  diminution. 

241.  What  said  of  the  periodical  variations  of  the  stars  ?  242.  What  other  remarka« 
ble  phenomenon?  What  instances  cited?  What  do  these  instances  prove?  243. 


J  36  ASTRONOMY. 

They  are  properly  called  Variable  Stars.  One  in  the  Wfiak  hab 
a  period  of  344  days  ".ad  is  remarkable  for  the  magnitude  of  its 
variations.  From  oeing  a  star  of  the  second  magnitude,  it 
becomes  so  dim  as  to  be  seen  with  difficulty  through  powerful 
telescopes.  Some  are  remarkable  for  the  shortness  of  the.  period 
of  their  variation.  Algol  has  a  period  of  between  two  and  three 
days  ;  Delta  Cephei,  of  5^-  days  ;  Beta  Lyra,  of  6  2-5  days  ; 
and  Mu  Antinoi,  of  7  days. 

The  regular  succession  of  these  variations  precludes  the  supposition  of  rn  actual 
destruction  of  the  stars;  neither  can  the  variations  be  supposed  to  arise  from  a  change 
of  distance  ;  for,  as  the  stars  invariably  retain  their  apparent  places,  it  would  be  neces- 
sary to  suppose  that  they  approach  to,  and  recede  from  the  earth  in  straight  lines, 
irhich  is  very  improbable.  The  most  probable  supposition  is,  that  the  stars  revolve,  like 
the  sun  and  planets,  about  an  axis.  "Such  a  motion,"  says  the  elder  Herschel,  "may 
be  as  evidently  proved,  as  the  diurnal  motion  of  the  earth.  Dark  spots,  or  large  por- 
tions of  the  surface,  less  luminous  than  the  rest,  turned  alternately  in  certain  directions, 
either  toward  or  from  us,  will  account  for  all  the  phenomena  of  periodical  changes  in  the 
luster  of  the  stars,  so  satisfactorily,  that  we  certainly  need  not  look  for  any  other  cause.'' 

DOUBLE  STAKS. 

244.  On  examining  the  stars  with  telescopes  of  considerable 
power,  many  of  them  are  found  to  be  composed  of  two  or  more 
stars,  placed  contiguous  to  each  other,  or  of  which  the  distance 
subtends  a  very  minute  angle.  This  appearance  is,  probably,  in 
many  cases,  owing  solely  to  the  optical  effect  of  their  position 
relative  to  the  spectator  ;  for  it  is  evident  that  two  stars  will 
appear  contiguous  if  they  are  placed  nearly  in  the  same  line  of 
vision,  although  their  real  distance  may  be  immeasurably  grea^, 

STARS  OPTICALLY  DOUBLE. 

Apparent  position.  True  position , 


-* 

B 

Here  the  observer  on  the  left  sees  a  large  and  small  star  at  A,  apparently  near  toge- 
ther—the lowest  star  being  much  the  smallest.  But  instead  of  their  being  situated  as 
tney  appear  to  be,  with  respect  to  each  other,  the  true  position  of  the  smaller  star  may 
be  at  B  instead  of  A;  and  the  difference  in  their  apparent  magnitudes  may  be  wholly 
owing  to  the  greater  distance  of  the  lower  star. 

Upon  this  subject  Dr.  Herschel  remarks,  that  this  nearness  of  the  stars  to  each  other, 
in  certain  cases,  might  be  attributed  to  some  accidental  cause,  did  it  occur  only  in  a  few 
instances ;  but  the  frequency  of  this  companionship,  the  extreme  closeness,  and,  in 
many  cases,  the  near  equality  of  the  stars  so  conjoined,  would  alone  lead  to  a  strong 
suspicion  of  a  more  near  and  intimate  relation  than  mere  casual  juxtaposition. 

245.  There  are,  however,  many  instances  in  which  the  angle 
of  position  of  the  two  stars  varies  in  such  a  manner  as  to  indi- 

arc  these  unsteady  stars  called  ?  What  specimens  referred  to,  and  their  periods  ?  What 
does  this  regular  succession,  Ac.,  prove?  What  theory  did  Dr.  Herschel  adopt  respect- 
ing the  variable  stars?  244.  What  said  of  double  stars?  Are  they  always  really  near 
each  other?  Illustrate  on  blackboard.  Remark  of  Dr.  llerschel?  245.  Are  they 


STARS  OPTICALLY  DOUBLE.  137 

cate  a  revolution  about  each  other  and  about  a  common  center. 
In  this  case  they  are  said  to  form  a  Binary  system  performing  to 
each  other  the  office  of  sun  and  planet,  and  are  connected 
together  by  laws  of  gravitation  like  those  which  prevail  in  the 
solar  system. 

The  recent  observations  of  Sir  John  Herschel  and  Sir  James  South,  hare  established  th- 
.ruth  of  this  singular  fact  beyond  a  doubt.  Motions  have  been  detected,  so  rapid  as  to 
become  measurable  within  very  short  periods  of  time ;  and  at  certain  epochs,  the  satellite 
or  feebler  star  has  been  observed  to  disappear,  either  passing  behind  or  before  the  primary 
or  approaching  so  near  to  it  that  its  light  has  been  absorbed  by  that  of  the  other. 

246.  The  most  remarkable  instance  of  a  regular  revolution  of 
this  sort,  is  that  of  Mizar,  in  the  tail  of  the  Great  Bear ;  in 
which  the  angular  motion  is  6  degrees  and  24  minutes  of  a  great 
circle,  annually  ;  so  that  the  two  stars  complete  a  revolution 
about  one  another  in  the  space  of  58£  years.     About  eleven 
twelfths  of  a  complete  circuit  have  been  already  described  since 
its  discovery  in  1781,  the  same  year  in  which  the  planet  Herschel 
was  discovered. 

A  double  star  in  Ophiuchus  presents  a  similar  phenomenon,  and 
the  satellite  has  a  motion  in  its  orbit  still  more  rapid.  Castor 
in  the  Twins,  Gamma  Virginis,  Zeta  in  the  Crab,  Zi  Bootis, 
Delta  Serpmtis,  and  that  remarkable  double  star  61  Cygnif 
together  with  several  others,  amounting  to  40  in  number,  exhi- 
bit the  same  evidence  of  a  revolution  about  each  other  and  about 
a  common  center.  (For  a  more  particular  description  of  these 
stars,  see  Telescopic  Objects  and  the  Map.) 

But  it  is  to  be  remembered  that  these  are  not  the  revolutions  of  bodies  of  a  planetary 
nature  around  a  solar  center,  but  of  sun  around  sun — each,  perhaps,  accompanied  by  its 
train  of  planets,  and  their  satellites,  closely  shrouded  from  our  view  by  the  splendor  of 
their  respective  suns,  and  crowded  into  a  space  bearing  hardly  a  greater  proportion  to 
the  enormous  interval  which  separates  them,  than  the  distances  of  the  satellites  of  our 
planets  from  their  primaries  bear  to  their  distances  from  the  sun  itself. 

247.  The  examination  of  double  stars  was  first  undertaken  by 
the  late  Sir  William  Herschel,  with  a  view  to  the  question  of 
parallax.     His  attention  was,  however,  soon   arrested   by  the 
new  and  unexpected  phenomena  which  these  bodies  presented. 

Sir  William  observed  of  them,  in  all,  2400.  Sir  James  South  and  Herschel  have  given  a 
catalogue  of  380  in  the  Transactions  of  the  Royal  Society  for  1824,  and  South  added  45S 
in  1826.  Sir  John  Herschel,  in  addition  to  the  above,  published  an  account  of  1000,  before 
he  left  England  for  the  Cape  of  Good  Hope,  where  he  went  to  push  his  discoveries  in  the 
southern  hemisphere.  Professor  Struve,  with  the  great  Dorpat  telescope,  has  given  a 
catalogue  of  3,063  of  the  most  remarkable  of  these  stars. 

The  object  of  these  catalogues  is  not  merely  to  fix  the  place  of  the  star  within  such  limits 
KS  will  enable  us  easily  to  discover  it  at  any  future  time,  but  also  to  record  a  description 

jver  really  near  each  other?  What  motion  ?  What  do  these  constitute?  Is  it  certain 
that  stars  are  ever  thus  in  motion  around  a  common  center  ?  246.  What  remarkable 
nstance  cited?  Its  annual  angular  motion?  Period?  What  Qther  binary  systems? 
Are  these  planetary  systems  like  our  own  ?  247.  Who  first  undertook  the  examination 
o.'t1)«  double  stars,  and  with  what  view?  What  number  dul  he  observe?  Wha*  catu- 


ASTRONOMY. 

of  the  appearance,  position,  and  mutual  distances  of  the  individual  stars  composing  the 
system,  in  order  that  subsequent  observers  may  have  the  means  of  detecting  their  con- 
nected motions,  or  any  changes  which  they  may  exhibit.  Professor  Struvj  has  also  taken 
notice  of  52  triple  stars,  among  which  No.  11  of  the  Unicorn,  Zeta  of  Cancer,  and  Zi  of 
the  Balance,  appear  to  be  ternary  systems  in  motion.  Quadruple  and  quintuple  stara 
have  likewise  been  observed,  which  also  appear  to  revolve  about  a  common  center  of 
gravity;  in  short,  every  region  of  the  heavens  furnishes  examples  of  these  curious  phe« 
nomena. 

COLOR  OF  THE  STARS. 

248.  Many  of  the  double  stars  exhibit  the  curious  and  beau- 
tiful phenomenon  of  contrasted  colors,  or  complimentary  tints.     In 
such  instances,  the  larger  star  is  usually  of  a  ruddy  or  orango 
hue,  while  the  smaller  one  appears  blue  or  green,  probably  in 
virtue  of  that  general  law  of  optics,  which  provides  that  when 
the  retina  is  under  the  influence  of  excitement  by  any  bright 
colored  light,  feebler  lights,  which,  seen  alone,  would  produce  no 
sensation   but   that   of  whiteness,    shall   for   the   time   appear 
colored  with  the  tint  complimentary  to  that  of  the  brighter. 

Thus,  a  yellow  color  predominating  in  the  light  of  the  brighter  star,  that  of  the  less 
bright  one,  in  the  same  field  of  view,  will  appear  blue;  while,  if  the  tint  of  the  brighter 
star  verge  to  crimson,  that  of  the  other  will  exhibit  a  tendency  to  green — or  even  appear 
a  vivid  green.  The  former  contrast  is  beautifully  exhibited  by  Iota,  in  Cancer ;  the  latter 
by  Al-tnaack,  in  Andromeda — both  fine  double  stars.  If,  however,  the  colored  star  be 
much  the  less  bright  of  the  two,  it  will  not  materially  affect  the  other.  Thus,  for  instance, 
Eta  Oassiopeiae  exhibits  the  beautiful  combination  of  a  large  white  star,  and  a  small  one 
of  a  rich  ruddy  purple. 

249.  It  is  not  easy  to  conceive  what  variety  of  illumination 
two  suns — a  red  and  a  green,  or  a  yellow  and  a  blue  one — must 
afford  to  a  planet  revolving  about  either  ;  and  what  charming 
contrasts  and  grateful  vicissitudes — a  red  and  a  green  day,  for 
instance,  alternating  with  a  white  one  and  with  darkness — might 
arise  from  the  presence  or  absence  of  one  or  the  other,  or  both, 
above  the  horizon. 

Insulated  stars  of  a  red  color,  almost  as  deep  as  that  of  blood,  occur  in  many  parts  of 
the  hsavens,  but  no  green  or  blue  star  (of  any  decided  hue)  has,  we  believe,  ever  beei. 
noticed,  unassociated  with  a  companion  brighter  than  itself. 


CLUSTERS  OF  STARS. 

250.  When  we  cast  our  eyes  over  the  concave  surface  of  the 
heavens  in  a  clear  night,  we  do  not  fail  to  observe  that  there  are, 
here  and  there,  groups  of  stars  which  seem  to  be  compressed 
together  more  densely  than  those  in  the  neighboring  parts  ; 
forming  bright  patches  or  clusters. 

•ogues?  Their  object?  What  triple  stars  ?  Ternary  systems  ?  Quadruple  stars,  Ac  ? 
248.  What  said  of  the  colors  of  the  stars?  What  law  of  optics  referred  to?  What  illua- 
'rations  ?  24S».  What  remarks  respecting  red  and  green  suns,  <fec.  ?  Of  insulated  star; 
of  a  red  color  f  250.  What  said  of  clusters  T  What  specimen  referred  to  ?  Pleiades  i 


NEBULA.  139 

The  Pleiades  are  an  instance  of  this  kind,  in  which  six  or 
seven  stars  may  be  seen  in  near  proximity,  by  the  naked  eye ; 
and  even  more  if  the  eye  be  turned  carelessly  upon  it;  for  it  is  a 
remarkable  fact  that  the  center  of  the  eye  is  far  less  sensible  to 
feeble  impressions  of  light,  than  the  exterior  portion  of  the  retina. 
Rheita  affirms  that  by  the  aid  of  a  telescope  he  counted  over  200 
stars  in  this  small  cluster.  See  Map  VIII.,  Fig.  28. 

In  the  constellation  called  Coma  Berenices  there  is  another  group 
more  diffused,  and  consisting  of  much  larger  stars.  In  Cancer 
there  is  a  nebulous  cluster  of  very  minute  stars,  called  Prasepe., 
or  the  Beehive,  which  is  sufficiently  luminous  to  be  seen  by  the 
naked  eye,  in  the  absence  of  the  moon,  and  which  any  ordinary 
spyglass  will  resolve  into  separate  stars.  In  the  sword-handle 
of  Perseus,  also,  is  another  such  spot,  crowded  with  stars.  It 
requires,  however,  rather  a  better  telescope  to  resolve  it  into 
individual  stars.  See  p.  65,  and  Map  VIII.,  Fig.  39. 

Whatever  be  the  nature  of  these  clusters,  it  is  certain  that  other  laws  of  aggregation 
prevail  in  them,  than  those  which  have  determined  the  scattering  of  starg  over  the  gene- 
ral surface  of  the  sky.  Many  of  them,  indeed,  are  of  an  exactly  round  figure,  and  con- 
vey the  idea  of  a  globular  space  filled  full  of  stars,  and  constituting,  in  itself,  a  family  or 
society  apart,  and  subject  only  to  its  own  internal  laws. 

''  It  would  be  a  vain  task,"  says  the  younger  Herschel,  "  to  attempt  to  count  the  stara 
in  one  of  these  globular  clusters.  They  are  not  to  be  reckoned  by  hundreds ;  for  it  would 
appear  that  many  clusters  of  this  description  must  contain,  at  least,  ten  or  twenty  thou- 
rvnd  stars,  compacted  and  wedged  together  in  a  round  space,  not  more  than  a  tenth  part 
as  la/**  as  that  which  is  covered  by  the  moon. 


NEBULAE. 

251.  The  Nebula,  so  called  from  their  dim,  cloudy  appearance, 
form  another  class  of  objects  which  furnish  matter  for  curious 
speculation  and  conjecture  respecting  the  formation  and  struc- 
ture of  the  sidereal  heavens.  When  examined  with  a  telescope 
of  moderate  powers,  the  greater  part  of  the  nebulae  are  dis- 
tinctly perceived  to  be  composed  of  little  stars,  imperceptible  to 
the  naked  eye,  because,  on  account  of  their  apparent  proximity, 
the  rays  of  light  proceeding  from  each  are  blended  together,  in 
such  a  manner  as  to  produce  only  a  confused  luminous  appear- 
ance. 

In  other  nebulae,  however,  no  individual  stars  can  be  perceived,  even  through  the  best 
telescopes ;  and  the  nebulae  exhibit  only  the  appearance  of  a  self-luminous  phosphores- 
cent patch  of  gaseous  vapor,  though  it  is  possible  that  even  in  this  case,  the  appearance 
may  be  owing  to  a  congeries  of  stars  so  minute,  or  so  distant,  as  not  to  afford,  singly, 
sufficient  light  to  make  an  impression  on  the  eye. 

Remarks  upon  their  nature  and  the  laws  that  govern  them?  Remarks  of  Herschel? 
251.  What  are  nebula,  and  why  so  called  ?  How  appear  through  telescopes?  Are  they 
all  resolvable  into  stars  ? 


140  ASTRONOMY. 

252.  One  of  the  most  remarkable  nebulaa  is  in  the  sword- 
handle  of  Orion.     It  is  formed  of  little  flocky  masses,  like  wisps 
of  cloud,  which  seem  to  adhere  to  many  small  stars  at  its  out- 
skirts.    It  is  not  very  unlike  the  mottling  of  the  sun's  disc,  but 
of  a  coarser  grain,  and  with  darker  intervals.     These  wisps  of 
light,  however,   present  no  appearance  of  being  composed  of 
small  stars  ;  but  in  the  intervals  between  them,  we  fancy  that 
we  see  stars,  or  that,  could  we  strain  our  sight  a  little  more,  we 
should  see  them.     These  intervals  may  be  compared  to  openings 
in  the  firmament,  through  which,  as  through  a  window,  we  seem 
to  get  a  glimpse  of  other  heavens,  and  brighter  regions,  beyond. 
See  page  45,  and  Map  VIII.,  Fig.  32. 

253.  Another  very  remarkable  nebula  is  that  in  the  girdle  of 
Andromeda,  which,  on  account  of  its  being  visible  to  the  naked 
eye,  has  been  known  since  the  earliest  ages  of  astronomy.     It  is 
often  mistaken  for  a  comet,   by  those  unacquainted  with  the 
heavens.     See  page  20,  and  Map  VIII.,  Fig.  22. 

Marias,  who  noticed  it  in  1612,  describes  its  appearance  as  that  of  a  candle  shining 
through  horn ;  and  the  resemblance  is  certainly  very  striking.  Its  form  is  a  long  oval, 
increasing,  by  insensible  gradations  of  brightness,  from  the  circumference  to  a  central 
point,  which,  though  very  much  brighter  than  the  rest,  is  not  a  star,  but  only  a  nebula  in 
a  high  state  of  condensation.  It  occupies  an  area  comparatively  large — equal  to  that 
of  the  moon  in  quadrature.  This  nebula  may  be  considered  as  a  type,  on  a  large  scale, 
of  a  very  numerous  class  of  nebulae,  of  a  round  or  oval  figure,  increasing  more  or  J«a?  in 
density  toward  the  center. 

254.  Annular  nebula  are  those  in  the  form  of  a  ring,  but  are 
among  the  rarest  objects  in  the  heavens.     The  most  conspicuous 
of  this  class  is  to  be  found  exactly  half-way  between  the  stars 
.Beta   and  Gamma  Lyrae,  and  may  be  seen  with  a  telescope  of 
moderate  power.     It  is  small,   and  particularly  well  denned  ; 
appearing  like  a  flat  oval  ring.     The  central  opening  is  not 
entirely  dark,  but  is  filled  with  a  faint,  hazy  light,  uniformly 
spread  over  it,  like  a  fine  gauze  stretched  over  a  hoop. 

255.  Planetary  nebula  are  very  extraordinary  objects.     They 
have,  as  their  name  imports,  the  appearance  of  planets,  with 
round  or  slightly  oval  discs,  somewhat  mottled,  but  approaching, 
in  some  instances,  to  the  vividness  of  actual  planets.     Some  of 
them,  upon  the  supposition  that  they  are  equally  distant  from  us 
with  the  stars,  must  be  of  enormous  magnitude.     That  one,  for 
instance,  which  is  situated  in  the  left  hand  of  Aquarius,  must 

252.  What  remarkable  nebula  mentioned?  Describe  it?  Point  out  on  the  map. 
258.  What  other?  How  long  known,  and  why?  Show  on  the  map.  How  described  by 
Alarms?  Its  form  and  extent?  How  considered?  254.  What  are  Annular  NebidcK  ? 
t>re  they  common?  What  specimen  referred  to?  255.  Planetary  nebulae?  Their 
aharacter  and  magnitude  ?  Specimen?  Stellar  nebulae  ?  General  remarks  respecting 


VIA    LACTEA.  141 

bave  a  volume  vast  enough,  upon  the  lowest  computation,  to  fill 
the  whole  orbit  of  Herschel  I 

In  some  instances  a  nebula  presents  the  appearance  of  a  faint, 
luminous  atmosphere,  of  a  circular  form,  and  of  large  extent, 
surrounding  a  central  star  of  considerable  brilliancy.  These  are 
denominated  Stellar  Nebula. 

The  nebulae  furnish  an  inexhaustible  field  of  speculation  and  conjecture.  That  by  far 
the  larger  number  of  them  consists  of  stars,  there  can  be  little  doubt;  and  in  the  inter- 
minable range  of  system  upon  system,  and  firmament  upon  firmament,  which  we  thus 
catch  a  glimpse  of,  the  imagination  is  bewildered  and  lost.  Sir  William  Herschel  con- 
jectured that  the  nebuUe  might  form  the  material  out  of  which  nature  elaborated  new 
suns  and  systems,  or  replenished  the  wasted  light  of  older  ones.  But  the  little  we  know 
of  the  physical  constitution  of  these  sidereal  masses,  is  altogether  insufficient  to  warrant 
Buch  a  conclusion.  (For  a  Spiral  Nebula  recently  discovered  by  Lord  Rosse,  see  Map  IX. 
Fig.  68.) 


CHAPTER  XIY. 

YIA  LACTEA  (THE  MILKY-WAT). 

"  Throughout  the  Galaxy's  extended  line, 
TJnnumber'd  orbs  in  gay  confusion  shine  : 
Where  every  star  that  gilds  the  gloom  of  night 
With  the  faint  tremblings  of  a  distant  light, 
Perhaps  illumes  some  system  of  its  own, 
With  the  strong  influence  of  a  radiant  sun." — Mrs.  Carter. 

256.  THE  YIA  LAC.TEA,  or  Milky-Way,  is  that  luminous  zone 
or  pathway  of  singular  whiteness,  varying  from  4°  to  20°  in 
width,  which  passes  quite  around  the  heavens.  The  Greeks 
called  it  GALAXY,  on  account  of  its  color  and  appearance  :  the 
Latins,  for  the  same  reason,  called  it  YIA  LACTEA,  which,  in  our 
tongue,  is  Milky-Way. 

Of  all  the  objects  which  ths  heavens  exhibit  to  our  view,  this  fills  the  mind  with  the 
most  indescribable  grandeur  and  amazement.  When  we  consider  what  unnumbered 
millions  of  mighty  suns  compose  this  stupendous  girdle,  whose  distance  is  so  vast  that 
the  strongest  telescope  can  hardly  separate  their  mingled  twilight  into  distinct  specks, 
and  that  the  most  contiguous  of  any  two  of  them  may  be  as  far  asunder  as  our  sun  is 
from  them,  we  fall  as  far  short  of  adequate  language  to  express  our  ideas  of  such  immen- 
uity,  as  we  do  of  instruments  to  measure  its  boundaries. 

'  257.  It  is  one  of  the  achievements  of  astronomy  that  has 
resolved  the  Milky-Way  into  an  infinite  number  of  small  stars, 
whose  confused  and  feeble  luster  occasions  that  peculiar  white- 
ness which  we  see  in  a  clear  evening,  when  the  moon  is  absent. 
It  is  also  a  recent  and  well-accredited  doctrine  of  astronomy., 

the  Nebulae?  Sir  Wm.  Herschel's  conjecture?  256.  What  is  the  Via  Lactea?  Its 
Greek  name?  What  said  of  its  magnificence  and  grandeur?  25T.  What  said  of  the 
achievements  of  astronomy  j1  Its  doctrine  respecting  the  structure  of  the  aciverk;i? 
Of  the  sun,  and  its  relation  to  the  fixed  stars? 


142  ASTRONOMY. 

that  all  the  stars  in  the  universe  are  arranged  into  clusters,  01 
groups,  which  are  called  NEBULA  or  STARRY  SYSTEMS,  each  of 
which  consists  of  myriads  of  stars. 

The  fixed  star  which  we  call  OUR  SUN,  belongs,  it  is  said,  to  that  extensive  nebula,  th<s 
Milky- Way;  and  although  apparently  at  such  an  inmeasurable  distance  from  its  fellows 
is,  doubtless,  as  near  to  any  one  of  them,  as  they  are  to  one  another. 

258.  Of  the  number  and  economy  of  the  stars  which  compose 
this  group,  we  have  very  little  exact  knowledge.     Dr.  Herschel 
informs  us  that,  with  his  best  glasses,  he  saw  and  counted  588 
stars  in  a  single  spot,  without  moving  his  telescope  ;  and  as  the 
gradual  motion  of  the  earth  carried  these  out  of  view  and  intro- 
duced others  successively  in  their  places,  while  he  kept  his  tele- 
scope steadily  fixed  to  one  point,  "  there  passed  over  his  field 
of  vision,  in  the  space  of  one  quarter  of  an  hour,  no  lest  than 
one  hundred  and  sixteen  thousand  stars,  and  at  another  time,  in 
forty-one  minutes,  no  less  than  two  hundred  and  fifty-eight  thou- 
sand." 

In  *,11  parts  of  the  Milky- Way  he  found  the  stars  unequally  dispersed,  and  appearing 
to  arrange  themselves  into  separate  clusters.  In  the  small  space  for  example,  between 
Beta  and  Sad'r,  in  Cygni,  the  stars  seem  to  be  clustering  in  two  divisions  ;  each  division 
conta  Jiing  upwards  of  one  hundred  and  sixty-five  thousand  stars.  At  other  observations, 
when  examining  a  section  of  the  Milky- Way,  not  apparently  more  than  a  yard  in  breadth, 
and  six  in  length,  he  discovered  fifty  thousand  stars,  large  enough  to  be  distinctly 
count  id  ;  and  he  suspected  twice  as  many  more,  which,  for  want  of  sufficient  light  in  his 
telescope,  he  saw  only  now  and  then. 

259.  It  appears  from  numerous  observations,  that  various 
changes  are  taking  place  among  the  nebulae — that  several  nebu- 
las are  formed  by  the  disolution  of  larger  ones,  and  that  many 
nebulae  of  this  kind  are  at  present  detaching  themselves  from 
the  Milky-Way.     In  that  part  of  it  which  is  in  the  body  of 
Scorpio,  ihere  is  a  large  opening,  about  4°  broad,  almost  desti 
tute  of  stars.     These  changes  seem  to  indicate  that  mighty 
movements  and  vast  operations  are  continually  going  on  in  the 
distant  regions  of  the  universe,  upon  a  scale  of  magnitude  and 
grandeur  which  baffles  the  human  understanding. 

More  than  two  thousand  five  hundred  nebulae  have  already  been  observed ;  and,  if 
each  of  them  contains  as  many  stars  as  the  Milky-Way,  several  hundreds  of  millions  of 
stars  must  exist,  even  within  that  portion  of  the  heavens  which  lies  open  to  our  obser- 
vation. 

"  0  what  a  confluence  of  ethereal  fires. 
From  urns  unnumber'd  down  the  steep  of  heaven 
Streams  to  a  point,  and  centers  on  my  sight." 

260.  Although  the  Milky-Way  is  more  or  less  visible  at  all 
seasons  of  the  year,  yet  it  is  seen  to  the  best  advantage  during 

258.  Number  and  economy  of  the  stars?  Dr.  Herschel's  statements?  What  number 
passed  the  field  of  his  instrument  in  a  quarter  of  an  hour?  In  forty-one  minutes?  In 
space  apparently  only  a  yard  in  breadth?  259.  What  changes  observed  in  the  nebu- 
las? What  do  they  indicate?  Number  of  nebulae?  Estimated  number  of  stars? 
^60.  When  is  the  Via  Lactea  »t«n  to  the  best  advantage?  Direction  when  Lyra  is  on  the 


ORIGIN    OF    THE    CONSTELLATIONS  143 

the  months  of  July,  August,  September,  and  October,  When 
Lyra  is  on,  or  near  the  meridian,  it  may  be  seen  stretching 
obliquely  over  the  heavens  from  northeast  to  southwest,  gradu- 
ally moving  over  the  firmament  in  common  with  other  constel- 
lations. (For  views  of  our  cluster,  see  Map  IX.,  Figs.  69,  70,  71.) 

Its  form,  treadth  and  appearance  are  various,  indifferent  parts  of  its  course.  In  some 
places  it  is  dense  and  luminous ;  in  others,  it  is  scattered  and  faint.  Its  breadth  is  often 
not  more  than  five  degrees ;  thouph  sometimes  it  is  ten  or  fifteen  degrees,  and  even 
twenty.  In  some  places  it  assumes  a  Double  path,  but  for  the  most  part  it  is  single. 

It  may  be  traced  in  the  heavens,  beginning  near  the  head  of  Cepheus,  about  30°  from 
the  north  pole,  through  the  constellations  Cassiopeia,  Perseus,  Auriga,  and  part  of  Orion 
and  the  feet  of  Gemini,  where  it  crosses  the  Zodiac ;  thence  over  the  equinoctial  into 
the  southern  hemisphere,  through  Monoceros,  and  the  middle  of  the  ship  Argo,  where  it 
is  most  luminous,  Charles'  Oak,  the  Cross,  the  feet  of  the  Centaur,  and  the  Altar.  Here 
it  is  divided  into  two  branches,  as  it  passes  over  the  Zodiac  again  into  the  northern  hem- 
isphere. One  branch  runs  through  the  tail  of  Scorpio,  the  bow  of  Sagittarius,  the  shield 
of  Sobieski,  the  feet  of  Antinous,  Aquila,  Delphinus,  the  Arrow  and  the  Swan.  Th'i  other 
branch  passes  through  the  upper  part  of  the  tail  of  Scorpio,  the  side  of  Serpentarius, 
Taurus  Poniatowskii,  the  Goose  and  the  neck  of  the  Swan,  where  it  again  unites  with  the 
other  branch,  and  passes  on  to  the  head  of  (Jepheus,  the  place  of  its  beginning. 

Some  of  the  pagan  philosophers  maintained  that  the  Milky- Way  was  formerly  the  sun's 
path,  and  that  its  present  luminous  appearance  is  the  track  which  its  scattered  beams 
left  visible  in  the  heavens. 

The  ancient  poets,  and  even  philosophers,  speak  of  the  Galaxy,  or  Milky-Way,  as  the 
path  which  their  deities  used  in  the  heavens,  and  which  led  directly  to  the  throne  of 
Jupiter.  Thus,  Ovid,  in  his  Metamorphoses,  Book  i.  :— 

"  A  way  there  is  in  heaven's  extended  plain, 
Which,  when  the  skies  are  clear,  is  seen  below, 
And  mortals,  by  the  name  of  Milky,  know ; 
The  groundwork  is  of  stars,  through  which  the  road 
Lies  open  to  the  Thunderer's  abode." 

Milton  alludes  to  this  in  the  following  lines  :— 

"  A  broad  and  ample  road,  whose  dust  is  gold, 
And  pavement,  stars,  as  stars  to  thee  appear, 

Seen  in  the  Galaxy,  that  Milky- Way,  * 

Which  nightly  as  a  circling  zone,  thou  seest 
Powdered  with  stars." 


CHAPTER  XY. 

ORIGIN    OF    THE     CONSTELLATIONS. 

261.  THE  science  of  astronomy  was  cultivated  by  the  imme- 
diate descendants  of  Adam.  JOSEPHUS  informs  us  that  the  sons 
of  SETH  employed  themselves  in  the  study  of  astronomy  ;  and 
that  they  wrote  their  observations  upon  two  pillars,  one  of  brick 

meridian?    Its  form,  breadth,  &c.?    How  traced  in  the  heavens?    Notion  of  the  Pagan 
philosophers  ?  Of  the  poets  ?  What  citations  ?    261.  How  early  was  astronomy  cultivated  ? 


i4i  ASTRONOMY. 

am  the  other  of  stone,*  in  order  to  preserve  them  against  the 
destruction  which  A  DAM  had  foretold  should  come  upon  the  earth. 

He  also  relates,  that  Abraham  argued  the  unity  and  poorer  of  God,  from  the  orderly 
course  of  things  both  at  sea  and  land,  in  their  times  and  seasons,  and  from  his  observa- 
tions upon  the  motions  and  influences  of  the  sun,  moon  and  stars  ;  and  that  he  read  lec- 
tures in  astronomy  and  arithmetic  to  the  Egyptians,  of  which  they  understood  nothing 
till  Abraham  brought  these  sciences  from  Chaldea  to  Egypt ;  from  whence  they  passed  ti> 
the  Greeks. 

262.  BEROSUS  also  observes  that  Abraham  was  a  great  and  just 
man,  and  famous  for  his  celestial  observations';  the  making  of 
which  was  thought  to  be  so  necessary  to  the  human  welfare,  that 
he  assigns  it  as  the  principal  reason  of  the  Almighty's  prolong- 
ing the  life  of  man. 

This  ancient  historian  tells  us,  in  his  account  of  the  longevity  of  the  antediluvians, 
that  Providence  found  it  necessary  to  prolong  man's  days,  in  order  to  promote  the  study 
and  advancement  of  virtue,  and  the  improvement  of  geometry  and  astronomy,  which 
required,  at  least,  six  hundred  years  for  making  and  perfecting  observations.t 

263.  When  Alexander  took  Babylon,  Calisthenes  found  that 
the  most  ancient  observations  existing  on  record  in  that  city, 
were  made  by  the  Chaldeans  about  1903  years  before  that  period, 
which  carries  us  back  to  the  time  of  the  dispersion  of  mankind 
by  the  confusion  of  tongues.     It  was  1500  years  after  this  that 
the  Babylonians  sent  to  Hezekiah,  to  inquire  about  the  shadow's 
going  back  on  the  dial  of  Ahaz. 

It  is,  therefore,  very  probable  that  the  Chaldeans  and  Egyptians  were  the  original 
inventors  of  astronomy;  but  at  what  period  of  the  world  they  marked  out  the  heavens 
into  constellations,  remains  in  uncertainty.  La  Place  fixes  the  date  thirteen  or  fourteen 
hundred  years  before  the  Christian  era,  since  it  was  about  this  period  that  Eudoxus  con- 
structed the  first  celestial  sphere  upon  which  the  constellations  were  delineated.  Sir 
Isaac  Newton  was  of  opinion,  that  all  the  old  constellations  related  to  the  Argonautic 
expedition,  and  that  they  were  invented  to  commemorate  the  heroes  and  events  of  that 
memorable  enterprise.  It  should  be  remarked,  however,  that  while  none  of  the  ancient 
constellations  refer  to  transactions  of  a  later  date,  yet  we  have  various  accounts  of  them 
of  a  much  higher  antiquity  than  that  event. 

264.  Some  of  the  most  learned  antiquarians  of  Europe  have 
searched  every  page  of  heathen  mythology,  and  ransacked  all 
the  legends  of  poetry  and  fable  for  the  purpose  of  rescuing  this 
subject  from  that  impermeable  mist  which  rests  upon  it,   and 
they  have  only  been  able  to  assure  us,  in  general  terms,  that 
they  are  Chaldean  or  Egyptian  hieroglyphics,  intended  to  per- 
petuate, by  means  of  an  imperishable  record,  the  memory  of  the 
times  in  which  their  inventors  lived,  their  religion  and  manners, 

*  Josephus  affirms,  that  "he  saw  himself  that  of  stone  to  remain  in  Syria  in  his  ow«) 
time." 
t  Vince's  Complete  System  of  Astronomy,  Vol.  ii.  p.  244. 


What  proof?  What  said  of  Abraham?  262.  What  further  proof?  What  reason 
assigned  for  the  longevity  of  the  antediluvians?  263.  What  discovery  by  Calisthenes  ? 
What  conclusion  from  this  discovery  ?  La  Place's  date  of  the  origin  of  the  constdla 
Uocs?  Sir  Isaac  Newton's  opinion?  Remark?  264.  What  researches,  and  wba', 
results? 


ORIGIN    OF    THE    CONSTELLATIONS.  145 

their  achievements  in  the  arts,  and  whatever  in  theh1  history  was 
•nost  worthy  of  being  commemorated.  There  was,  at  least,  a 
moral  grandeur  in  this  idea  ;  for  an  event  thus  registered,  a 
custom  thus  canonized,  or  thus  enrolled  among  the  stars,  must 
needs  survive  all  other  traditions  of  men,  and  stand  forth  in  per- 
petual characters  to  the  end  of  time. 

265.  In  arranging  the  constellations  of  the  Zodiac,  for  instance, 
it  would  be  natural  for  them,  we  may  imagine,  to  represent 
those  stars  which  rose  with  the  sun  in  the  spring  of  the  year,  by 
such  animals  as  the  shepherds  held  in  the  greatest  esteem  at  that 
season  ;  accordingly,  we  find  Aries,  Taurus,  and  Gemini,  as  the 
symbols  of  March,  April,  and  May. 

266.  When  the  sun  enters  the  sign  Cancer,  at  the  summer 
solstice,  he  discontinues  his  progress  towards  the  north  pole,  and 
begins  to  return  towards  the  south  pole.     This  retrograde  mo- 
tion was  fitly  represented  by  a  Crab,  which  is  said  to  go  back- 
ward.    The  sun  enters  this  sign  about  the  22d  of  June. 

The  heat  which  usually  follows  in  the  next  mouth  was  repre- 
sented by  the  Lion  ;  an  animal  remarkable  for  its  fierceness, 
and  which  at  this  season  was  frequently  impelled  by  thirst  tc 
leave  the  sandy  desert,  and  make  its  appearance  on  the  banks 
of  the  Nile. 

267.  The  sun  entered  the  sixth  sign  about  the  time  of  harvest, 
which  season  was  therefore  represented  by  a  Virgin,  or  female 
reaper,  with  an  ear  of  corn  in  her  hand. 

At  the  autumnal  equinox,  when  the  sun  enters  Libra,  the 
days  and  nights  are  equal  all  over  the  world,  and  seem  to 
observe  an  equilibrium  or  balance.  The  sign  was  therefore 
represented  under  the  symbol  of  a  pair  of  Scales. 

268.  Autumn,  which  produces  fruit  in  great  abundance,  brings 
with  it  a  variety  of  diseases,  and  on  this  account  was  represented 
by  that  venomous  animal,   the  Scorpion,  which,  as  he  recedes, 
wounds  with  a  sting  in  his  tail.     The  fall  of  the  leaf,  was  the 
season  for  hunting,  and  the  stars  which  mark  the  sun's  path  at 
this  time  were  represented  by  a  huntsman,  or  archer,  with  his 
arrows  and  weapons  of  destruction. 

The  Goat,  which  delights  in  climbing  and  ascending  some 
mountain  or  precipice,  is  the  emblem  of  the  winter  solstice,  when 
the  sun  begins  to  ascend  from  the  southern  tropic,  and  gradually 
to.  increase  in  height  for  the  ensuing  half  year. 


265.  Origin  of  Aries,  Taurus,  and  Gemini?        266.  Of  Cancer  and  Leo          2C7.  0' 
Virgo  aud  Libra  T        268.  Of  Scorpio  aud  Capricorn  ? 


1 46  ASTRONOMY. 

269.  Aquarius,  or  the  Water  Bearer,  is  represented  by  the 
figure  of  a  man  pouring  out  water  from  an  urn,  an  emblem  of 
the  dreary  and  uncomfortable  season  of  winter. 

The  last  of  the  zodiacal  constellations  was  Pisces,  or  a  couple 
of  fishes,  tied  back  to  back,  representing  the  fishing  season. 
The  severity  of  winter  is  over  ;  the  flocks  do  not  afford  suste- 
nance, but  the  seas  and  rivers  are  open  and  abound  with  fish. 

"  Thus  monstrous  forms,  o'er  heaven's  nocturnal  arch, 
Seen  by  the  sage,  in  pomp  celestial  march  ; 
See  Aries  there  his  glittering  bow  unfold, 
And  raging  Taurus  toss  his  horns  of  gold ; 
With  bended  bow  the  sullen  Archer  lowers, 
And  there  Aquarius  comes  with  all  his  showers ; 
Lions  and  Centaurs,  Gorgons,  Hydras  rise, 
And  gods  and  heroes  blaze  along  the  skies." 

Whatever  may  have  led  to  the  adoption  of  these  rude  names  at  first,  they  are  now 
retained  to  avoid  confusion. 

The  early  Greeks,  however,  displaced  many  of  the  Chaldean  constellations,  and  sub- 
stituted such  images  in  their  place  as  had  a  more  special  reference  to  their  own  history. 
The  Romans  also  pursued  the  same  course  with  regard  to  their  history;  and  henci  tho 
contradictory  accounts  that  have  descended  to  later  times. 

270.  Some,  moreover,  with  a  desire  to  divest  the  science  of 
the  stars  of  its  pagan  jargon  and  profanity,  have  been  induced 
to  alter  both  the  names  and  figures  of  the  constellations.     In 
doing   this,   they  have,  committed  the  opposite  fault ;  that  of 
blending  them  with  things  sacred. 

The  "  venerable  Bede,"  for  example,  instead  of  the  profane 
names  and  figures  of  the  twelve  constellations  of  the  Zodiac, 
substituted  those  of  the  twelve  apostles.  Julius  Schillerius,  fol- 
lowing his  example,  completed  the  reformation  in  1627,  by  giv- 
ing Scripture  names  to  all  the  constellations  in  the  heavens. 

Weigelius,  too,  a  celebrated  professor  of  mathematics  in  the  University  of  Jena,  made 
a  new  order  of  constellations,  by  converting  the  firmament  into  a  COSLUM  HERALDICUM,  in 
which  he  introduced  the  arms  of  all  the  princes  of  Europe.  But  astronomers,  generally, 
never  approved  of  these  innovations ;  and  for  ourselves,  we  had  as  lief  the  sages  and 
heroes  of  antiquity  should  continue  to  enjoy  their  fianced  honors  in  the  sky,  as  to  see 
their  places  supplied  by  the  princes  of  Europe. 

271.  The  number  of  the  old  constellations,  including  those  of 
the  Zodiac,  was  only  forty-eight.      As  men   advanced  in  the 
knowledge  of  the  stars,  they  discovered  many,  but  chiefly  in 
southern  latitudes,  which  were  noc  embraced  in  the  old  constel- 
lations, and  hence  arose  that  mixture  of  ancient  and  moderr 
names  which  we  meet  with  in  modern  catalogues. 

272.  Astronomers  divide  the  heavens  into  three  parts,  called 
the  Northern  and  Southern  Hemispheres,  and  the  Zodiac.  In  the 

269.  Of  Aquarius  and  Pisces?    Course  of  the  Greeks  and  Romans,  in  displacing  con- 
stellations?       270.  What  other  reform  attempted?    What  particular  instances  cited! 
Bede  ?     Schillerius  ?     Weigelius  ?     How  are  these  innovations  regarded  by  astronomers 
211.  Number  of  the  old  constellations?    How  others  added?        272.  How  do  astrono 


ORIGIN    OF    THE    CONSTELLATIONS.  147 

northern  hemisphere,  astronomers  usually  reckon  thirty-four  con- 
stellations, in  the  Zodiac  twelve,  and  in  the  southern  hemisphere 
forty-seven  ;  making  in  all  ninety-three.  Besides  these,  there 
are  a  few  of  inferior  note,  recently  formed,  which  are  not  con- 
sidered sufficiently  important  to  be  particularly  described. 

273.  About  the  year  160*3,  John  Bayer,  a  native  of  Germany, 
invented  the  convenient  system  of  denoting  the  stars  in  each 
constellation  by  the  letters  of  the  Greek   alphabet,  applying  to 
the   largest   star  the  first  letter  of  the  alphabet ;  to  the  next 
largest  the  second  letter,  and  so  on  to  the  last.     Where  there 
are  more  stars  in  the  constellation  than  there  are  Greek  letters, 
the  remainder  are  denoted  by  the  letters  of  the  Roman  alphabet, 
and  sometimes  by  figures. 

By  this  system  of  notation,  it  is  now  as  easy  to  refer  to  any  particular  star  in  the 
heavens,  as  to  any  particular  house  in  a  populous  c'ty,  by  its  street  and  number.  Before 
this  practice  was  adopted,  it  was  customary  to  denote  the  stars  by  referring  them  to 
their  respective  situations  in  the  figure  of  the  constellation  to  which  they  severally 
belonged,  as  the  head,  the  arm,  the  foot,  &c. 

It  is  hardly  necessary  to  remark  that  these  figures,  which  are  all  very  curiously  depicted 
upon  artificial  globes  and  maps,  are  purely  a  fanciful  invention — answering  many  con- 
venient ends,  however,  for  purposes  of  reference  and  classification,  as  they  enable  us  to 
designate  with  facility  any  particular  star,  or  cluster  of  stars ;  though  these  clusters 
very  rarely,  if  ever,  represent  the  real  figures  of  the  objects  whose  names  they  bear. 
And  yet  it  is  somewhat  remarkable  that  the  name  of  "  Great  Bear,"  for  instance,  should 
have  been  given  to  the  very  same  constellation  by  a  nation  of  American  aborigines  (the 
Iroquois),  and  by  the  most  ancient  Arabs  of  Asia,  when  there  never  had  been  any  com- 
munication between  them !  Among  other  nations,  also,  between  whom  there  exists  no 
evidence  of  any  intercourse,  we  find  the  Zodiac  divided  into  the  same  number  of  constel- 
lations, and  these  distinguished  by  nearly  the  same  names,  representing  the  twelve 
months,  or  seasons  of  the  year. 

274.  The  constellations,  or  the  uncouth  figures  by  which  they 
are  represented,  are  a  faithful  picture  of  the  ruder  stages  of 
civilization.     They  ascend  to  times  of  which  no  other  record 
exists  ;  and  are  destined  to  remain  when  all  others  shall  be  lost. 
Fragments  of  history,  curious  dates  and  documents  relating  to 
chronology,  geography  and  languages,   are  here   preserved  in 
imperishable  characters. 

The  adventures  of  the  gods,  and  the  inventions  of  men,  the  exploits  of  heroes,  and 
the  fancies  of  poets,  are  here  spread  out  in  the  heavens,  and  perpetually  celebrated  before 
all  nations.  The  Seven  stars,  and  Orion,  present  themselves  to  us,  as  they  appeared  to 
Amos  and  Homer:  as  they  appeared  to  Job,  more  than  3000  years  ago,  when  the 
Almighty  demanded  of  him — "  Knowest  thou  the  ordinances  of  heaven?  Canst  thou 
bind  the  sweet  influences  of  the  PLEIADKS,  or  loose  the  bands  of  ORION?  Canst  thou 
bring  forth  MAZZAROTH  in  his  season,  or  canst  thou  guide  ARCTURUS  with  his  sons?" 
Here,  too,  are  consecrated  the  lyre  of  Orpheus  and  the  ship  of  the  Argonauts  ;  and,  in 
the  same  firmament,  glitter  the  Mariner's  Compass  and  the  Telescope  of  Herschel. 

mers  divide  the  constellations?  Number  in  each  division?  Total?  What  other* . 
2T3.  John  Bayer's  invention?  Utility  of  it?  How  before  it  was  adopted  r  What  remark 
respecting  the  figures  on  maps  and  globes,  and  their  use?  What  remarkable  facto 
etatcd?  274.  Historical  use  of  the  constellations?  Illustrations? 


B.G. 


148  ASTRONOMY. 

CHAPTER  XVI. 
NUMBER,  DISTANCE  AND  ECONOMY  OF  THE  STARS. 

275.  THE  first  conjecture  in  relation  to  the  distance  of  the 
fixed  stars  is,  that  they  are  all  placed  at  an  equal  distance  from 
the  observer,  upon  the  visible  surface  of  an  immense  concave 
vault,  which  rests  upon  the  circular  boundary  of  the  world,  and 
which  we  call  the  Firmament.     We  can,  with  the  unassisted  eye, 
form  no  estimate  of  their  respective  distances  ;  nor  has  the  tele- 
scope yet  enabled  us  to  arrive  at  any  exact  results  on  this  sub- 
ject, although  it  has  revealed  to  us  many  millions  of  stars  that 
are  as  far  removed  beyond  those  which  are  barely  visible  to  the 
naked  eye,  as  these  are  from  us. 

Viewed  through  the  telescope,  the  heavens  become  quite  another  spectacle — not  only 
to  the  understanding  but  to  the  senses.  New  worlds  burst  upon  the  sight,  and  old  onea 
expand  to  a  thousand  times  their  former  dimensions.  Several  of  those  little  stars  which 
but  feebly  twinkle  on  the  unassisted  eye,  become  immense  globes,  with  land  and  water, 
mountains  and  valleys,  encompassed  by  atmospheres,  enlightened  by  moons,  and  diver- 
sified by  day  and  night,  summer  and  winter. 

Beyond  these  are  other  suns,  giving  light  and  life  to  other  systems,  not  a  thousand,  or 
two  thousand  merely,  but  multiplied  without  end,  and  ranged  all  around  us,  at  immense 
distances  from  each  other,  attended  by  ten  thousand  times  ten  thousand  worlds,  all  in 
rapid  motion  ;  yet  calm,  regular  and  harmonious — all  space  seems  to  be  illuminated,  and 
every  particle  of  light  a  world. 

276.  It  has  been  computed  that  one  hundred  millions  of  stars 
which  cannot  be  discerned  by  the  naked  eye,  are  now  visible 
through  the  telescope.     And  yet  all  this  vast  assemblage  of  suns 
and  worlds  may  bear  no  greater  proportion  to  what  lies  beyond 
the  utmost  boundaries  of  human  vision,  than  a  drop  of  water  to 
the  ocean  ;  and,   if  stricken  out  of  being,  would  be   no  more 
missed,  to  an  eye  that  could  take  in  the  universe,  than  the  fall 
of  a  single  leaf  from  the  forest. 

We  should  therefore  learn,  says  Dr.  Chalmers,  not  to  look  on  our  earth  as  the  universe 
of  God,  but  as  a  single,  insignificant  atom  of  it ;  that  it  is  only  one  of  the  many  mansions 
which  the  Supreme  Being  has  created  for  the  accommodation  of  his  worshipers ;  and 
that  he  may  now  be  at  work  in  regions  more  distant  than  geometry  ever  measured,  creat- 
ing won  Is  more  manifold  than  numbers  ever  reckoned,  displaying  his  goodness,  and 
spreading  over  all  the  intimate  visitations  of  his  care. 

277.  The  immense  distance  at  which  the  nearest  stars  are 
known  to  be  placed,  proves  that  they  are  bodies  of  a  prodigious 
size,  not  inferior  to  our  sun,  and  that  they  shine,  not  by  reflected 
rays,  but  by  their  own  native  light.     It  is  therefore  concluded, 

275.  What  is  the  first  conjecture  as  to  the  distance  of  the  stars?  Can  we  form  no  jus! 
estimate?  What  said  of  the  heavens  when  seen  through  a  telescope?  276.  What 
computation  as  to  ths  number  of  stars  invisible  to  the  naked  eye,  but  visible  through 
tt.lcscopce?  Is  this  probably  the  whole  universe  ?  Remark  of  Chalmers?  277.  Whar 


NUMBER,    DISTANCE,    AND    EC     NOMY    OB     THE    STARS.    149 

with  good  reason,  that  every  fixed  star  is  a  sun,  no  less  spacious 
than  ours,  surrounded  by  a  retinue  of  planetary  worlds,  which 
revolve  around  it  as  a  center,  and  derive  from  it  light  and  heat, 
and  the  agreeable  vicissitudes  of  day  and  night. 

These  vast  globes  of  light,  then,  could  never  have  been  designed  merely  to  diversify 
the  voids  of  infinite  space,  nor  to  shed  a  few  glimmering  rays  on  our  far  distant  world, 
for  the  amusement  of  a  few  astronomers,  who,  but  for  the  most  powerful  telescopes,  had 
never  seen  the  ten  thousandth  part  of  them.  We  may  therefore  rationally  conclude,  tha: 
wherever  the  All-wise  Creator  has  exerted  his  creative  power,  tJiere  also  he  has  placed 
intelligent  beings  to  adore  his  goodness. 

278.  The  greatest  possible  ingenuity  and  pains  have  been 
taken  by  astronomers  to  determine,  at  least,  the  approximate 
distance  of  the  nearest  fixed  stars.     If  they  have  hitherto  been 
unable  to  arrive  at  any  satisfactory  result,  they  have,  at  least, 
established  a  limit  beyond  which  the  stars  must  necessarily  be 
placed.     If  they  have  failed  to  calculate  their  true  distances 
from  the  earth,  it  is  because  they  have  not  the  requisite  data. 
The  solution  of  the  problem,  if  they  had  the  data,  would  not  be 
more  difficult  than  to  compute  the   relative   distances  of  the 
planets — a  thing  which  any  schoolboy  can  do. 

In  estimating  so  great  a  distance  as  the  nearest  fixed  star,  it  is  necessary  that  we 
employ  the  longest  measure  which  astronomy  can  use.  Accordingly,  we  take  the  whole 
diameter  of  the  earth's  orbit,  which,  in  round  numbers,  is  190  millions  of  miles,  and 
endeavor,  by  a  simple  process  in  mathematics,  to  ascertain  how  many  measures  of  this 
length  are  contained  in  the  mighty  interval  which  separates  us  from  the  stars. 

The  method  of  doing  this  can  be  explained  to  the  apprehension  of  the  pupil,  if  he  doe* 
not  shrink  from  the  illustration,  through  an  idle  fear  that  it  is  beyond  his  capacity. 

For  example  ;  suppose  that,  with  an  instrument  constructed  for  the  purpose,  we  should 
this  night  take  the  precise  bearing  or  angular  direction  from  us  of  some  star  in  the 
northern  hemisphere,  and  note  it  down  with  the  most  perfect  exactness,  and,  having 
waited  just  six  months,  when  the  earth  shall  have  arrived  at  the  opposite  point  of  its 
orbit,  190  millions  of  miles  east  of  the  place  which  we  now  occupy,  we  should  then  repeat 
our  observation  upon  the  same  star,  and  see  how  much  it  had  changed  its  position  by 
our  traveling  so  great  a  distance  one  side  of  it.  Now,  it  is  evident,  that  if  it  changes  its 
apparent  position  at  all,  the  quantity  of  the  change  will  bear  some  proportion  to  the 
distance  gone  over ;  that  is,  the  nearer  the  star,  the  greater  the  angle ;  and  the  more 
remote  the  star,  the  less  the  angle.  It  is  to  be  observed,  that  the  angle  thus  four'!,  i? 
called  the  star's  Annual  Parallax. 

279.  But  it  is  found  by  the  most  eminent  astronomers  of  the 
age,  and  the  most  perfect  instruments  ever  made,  that  the  paral- 
lax of  the  nearest  stars  does  net  exceed  ihefour  thousandth  part 
of  a  degree,  or  a  single  second  ;  so  that,  if  the  whole  great  orbit 
of  the  earth  were  lighted  up  into  a  globe  of  fire  600  millions  of 
miles  in  circumference,  it  would  be  seen  by  the  nearest  star  only 
as  a  twinkling  atom  ;  and  to  an  observer  placed  at  this  distance, 

proof  that  the  stars  are  large  bodies?  What  conclusion,  therefore?  What  other 
inference  ?  278.  What  effort  to  determine  the  distances  of  the  stars  ?  What  results  ? 
What  necessary  in  estimating  the  distances  of  the  stars  ?  What  measure  taken  ?  De 
scribe  the  process  of  determining  the  distance  of  the  stars  by  parallax.  279.  Wha 
ib  the  parallax  of  the  stars  found  to  be,  and  what  follows  as  a  consequence  ?  What 


,5H  ASTRONOMY. 

our  sun,  with  its  whole  retinue  of  planetary  worlds,  would  occupy 
a  space  scarcely  exceeding  the  thickness  of  a  spider's  web.* 

If  the  nearest  of  the  fixed  stars  are  placed  at  such  inconceivable  distances  in  tho 
regions  of  space,  with  what  line  shall  we  measure  the  distance  of  those  which  are  a  thou- 
eand  or  a  million  of  times  as  much  farther  from  them,  as  these  are  from  us  ? 

280.  If  the  annual  parallax  of  a  star  were  accurately  known, 
it  would  be  easy  to  compute  its  distance  by  the  following  rule  : 

As  the  sine  of  the  star's  parallax  : 

Is  to  radius,  or  ninety  degrees  :  : 

So  is  the  earth's  distance  from  the  sun : 

To  the  star's  distance  from  the  sun. 

If  we  allow  the  annual  parallax  of  the  nearest  star  to  be  1", 
the  calculation  will  be, 
As  0.0000048481368=Nat.  Sine  of  1". 
Is  to  1.0000000000000=Nat.  Sine  of  90°. 
So  is  95, 273,868. 867748554=Earth's  distance  from  the  sun 
To  19,651,627, 683,449=Star's  distance  from  the  sun. 

In  this  calculation  we  have  supposed  the  earth  to  be  placed  at  the  mean  distance  of 
34,047  of  its  own  semi-diameters,  or  95,273,868.867748554  miles  from  the  sun,  which  makes 
the  star's  distance  a  very  little  less  than  twenty  billions  of  miles.  Dr.  Herschel  says 
i  hat  Sirius  cannot  be  nearer  than  100,000  times  the  diameter  of  the  earth's  orbit,  or 
19,007,788,800,000  of  miles. 

Biot,  who  either  takes  the  earth's  distance  greater  than  he  lays  it  down  in  his  Traite 
Elementaire  d'Astronomie  Physique,  or  has  made  an  error  in  figures,  makes  the  dis- 
tance 20,086,868,036,404.  Dr.  Brewster  makes  it  20,159,665,000,000  miles.  A  mean  of 
these  computations,  is  20  billions  ;  that  is,  20  millions  of  millions  of  miles  to  a  parallax 
of  1'. 

Astronomers  are  generally  agreed  in  the  opinion  that  the  annual  parallax  of  the  stars 
is  less  than  1",  and  consequently  that  the  nearest  of  them  is  placed  at  a  much  greater 
distance  from  us,  than  these  calculations  make  it.  It  was,  however,  announced  in  1832, 
that  M.  d'Assas,  a  French  astronomer,  had  satisfactorily  established  the  annual  parallax 
of  Keid  (a  small  star  8°  N.  of  Gamma  Eridani),  to  be  2',  that  of  Rigel,  in  Orion,  to  be 
1".43,  and  that  of  Sirius  to  be  1".24.  If  these  results  could  be  relied  on,  Keid  would  be 
but  10  billions,  Rigel  but  14  billions,  and  Sirius  16  billions  of  miles  from  the  earth.  Ttiis 
latter  distance  is,  however,  so  great  that,  if  Sirius  were  to  fall  toward  the  earth  at 
the  rate  of  a  million  of  miles  a  day,  it  would  take  it  forty-three  thousand,  three  hundred 
years  to  reach  the  earth ;  or,  if  the  Almighty  were  now  to  blot  it  out  of  the  heavens,  its 
brilliance  wpuld  continue  undiminished  in  our  hemisphere  for  the  space  of  three  years 
to  come. 

*  A  just  idea  of  the  import  of  this  term,  will  impart  a  force  and  sublimity  to  an  expres- 
sion of  St.  James,  which  no  power  of  words  could  improve.  It  is  said,  chapter  i.  verse 
17,  of  Him  from  whom  cometh  down  every  good  and  perfect  gift,  that  there  is  "  QVK  £Vt 
7i apa/l/lay?/  TJ  Tpoirqs  airoaKiaafxa."  Literally,  there  is  "neither  parallax  nor 
s/uidow  of  change :"  As  if  the  apostle  had  said — Peradventure,  that  in  traveling  millions 
and  millions  of  miles  through  the  regions  of  immensity,  there  may  be  a  sensible  parallax 
to  some  of  the  fixed  stars  ;  yet,  as  to  the  Father  of  Lights,  view  him  from  whatever  point 
of  his  empire  we  may,  he  is  without  parallax  or  shadow  of  change  I 

then,  of  the  mo«»  distant  stars?  280.  How  deduce  the  distance  of  a  star  from  its 
parallax,  if  known  >  Computation  laid  down  ?  Dr.  Herschel's  remark?  Riot's  estimate? 
Dr.  Brewster's?  The  mean  of  these  three  estimates  ?  Are  astronomers  agreed  as  to  thy 
i.;rjvliax  of  the  stars?  .M.  d'Assas'  computation*  :unl  n-sults? 


NUMBER,  DISTANCE,  AJND  ECONOMY  OF  THE  STARS.  16} 

281.  The  most  brilliant  stars,  till  recently,  were  supposed  to 
be  situated  nearest  the  earth,  but  later  observations  prove  that, 
this  opinion  is  not  well  founded,  since  some  of  the  smaller  stars 
appear  to  have  not  only  a  greater  annual  parallax,  but  an 
absolute  motion  in  space,  much  greater  than  those  of  the  bright- 
est class. 

282.  It  has  been  computed  that  the  light  of  Sirius,  although 
twenty  thousand  million  times  less  than  that  of  our  sun,  is  never- 
theless three  hundred  and  twenty-four  times  greater  than  that  of 
a  star  of  the  6th  magnitude.     If  we  suppose  the  two  stars  to 
be  really  of  the  same  size,  it  is  easy  to  show  that  the  star  of  the 
sixth  magnitude  is  fifty-seven  and  one-third  times  farther  from  us 
than  Sirius  is,  because  light  diminishes  as  the  square  of  the  dis- 
tance of  the  luminous  body  increases. 

By  the  same  reasoning  it  may  be  shown,  that  if  Sirius  were  placed  where  the  sun  is,  t 
would  appear  to  us  to  be  four  times  as  large  as  the  sun,  and  give  four  times  as  much  light 
and  heat.  It  is  by  no  means  unreasonable  to  suppose,  that  many  of  the  fixed  starb 
exceed  a  million  of  miles  in  diameter. 

283.  We  may  pretty  safely  affirm,  then,  that  stars  of  the 
sixth  magnitude  are  not  less  than  nine  hundred  millions  of  millions 
of  miles  distant  from  us  ;  or  a  million  of  times  farther  from  us  than 
the  planet  Saturn,  which  is  scarcely  visible  to  the  naked  eye. 
But  the  human  mind  in  its  present  state  can  no  more  appreciate 
such  distances  than  it  can  infinity  ;  for  if  our  earth,  which  moves 
at  more  than  the  inconceivable  velocity  of  a  million  and  a  half 
of  miles  a  day,  were  to  be  hurried  from  its  orbit,  and  to  take  the 
same  rapid  flight  over  this  immense  tract,  it  would  not  traverse 
it  in  sixteen  hundred  thousand  years ;  and  every  ray  of  light, 
although  it  moves  at  the  rate  of  one  hundred  and  ninety-three 
thousand  miles  in  a  single  second  of  time,  is  more  than  one  hun- 
dred and  seventy  years  in  coming  from  the  star  to  us. 

But  what  is  even  this,  compared  with  that  measureless  extent  which  the  discoveries  of 
the  telescope  indicate?  According  to  Dr.  Herschel,  the  light  of  some  of  the  nebulae,  jusl 
perceptible  through  his  40  feet  telescope,  must  have  been  a  million  of  ages  in  coming  tj 
the  earth ;  and  should  any  of  them  be  now  destroyed,  they  would  continue  to  be  percep- 
tible for  a  trillion  of  ages  to  come. 

Dr.  Hersrhel  informs  us,  that  the  glass  which  he  used  would  separate  stars  at  497  times 
the  distance  of  Sirius. 

284.  It  is  one  of  the  wonders  of  creation,  that  any  phenomena 
of  bodies  at  such  an  immense  distance  from  us  should  be  percep- 
tible by  human  sight ;  but  it  is  a  part  of  the  Divine  Maker's 

281.  Former  supposed  relative  distance  of  the  most  brilliant  stars  ?  Present  opinion, 
und  on  what  founded?  282.  What  computation  as  to  the  light  of  Sirius?  What  con- 
clusion as  to  the  distance  of  other  stars  ?  How,  then,  would  he  appear  if  as  near  as  ou  : 
hun?  What  conclusion  as  to  the  magnitude  of  the  stars?  283.  Distance  of  the  sixth 
magnitude  stars ?  How  measured  by  the  flight  of  the  earth ?  Of  light?  What  further 
estimate  by  Dr.  Herschel  ?  284.  What  remark  respecting  our  knowledge  of  the  start 


>  52  ASTRONOMY. 

plan,  that  although  they  do  not  act  physically  upon  us,  yet  tliey 
should  so  far  be  objects  of  our  perception,  as  to  expand  our  ideas 
of  the  vastness  of  the  universe,  and  of  the  stupendous  extent 
and  operations  of  his  omnipotence. 

"  With  these  facts  before  us,"  says  an  eminent  astronomer  and  divine,  "  it  is  most  rea- 
sonable to  conclude,  that  those  expressions  in  the  Mosaic  history  of  Creation,  which 
relate  to  the  creation  of  the  fixed  stars,  are  not  to  be  understood  as  referring  to  the  time 
when  they  were  brought  into  existence,  as  if  they  had  been  created  about  the  same  time 
with  our  earth  ;  but  as  simply  declaring  the  fact,  that,  at  whatever  period  in  duration 
they  were  created,  they  derived  their  e&istenee  from,  God." 

285.  "That  the  stars  here  mentioned"  (Gen.  i.  16),  says  a 
distinguished  commentator,  "were  the  planets  of  our  system, 
and  not  the  fixed  stars,  seems  a  just  inference  from  the  fact,  that 
after   mentioning    them,    Moses    immediately    subjoins,    *  And 
Elohim  set  them  in  the  firmament  of  the  heaven  to  give  light 
upon  the  earth,  and  to  rule  over  the  day  and  over  the  night  ;' 
evidently  alluding  to  Yenus  and  Jupiter,  which  are  alternately 
our  morning  and  evening  stars,  and  which  '  give  light  upon  the 
earth/  far  surpassing  in  brilliancy  any  of  the  fixed  stars." 

However  vast  the  universe  now  appears,  however  numerous  the  worlds  which  may 
exist  within  its  boundless  range,  the  language  of  Scripture,  and  Scripture  alone,  is  suffi- 
ciently comprehensive  and  sublime  to  express  all  the  emotions  which  naturally  arise  in 
the  mind  when  contemplating  its  structure.  This  shows  not  only  the  harmony  which 
subsists  between  the  discoveries  of  the  Revelation  and  the  discoveries  of  Science,  but 
also  forms,  by  itself,  a  strong  presumptive  evidence,  that  the  records  of  the  Bible  arc 
authentic  and  divine. 

286.  We  have  hitherto  described  the  stars  as  being  immov- 
able and  at  rest  ;  but  from  a  series  of  observations  on  double 
stars,  Dr.  Herschel   found   that   a   great  many  of  them  have 
changed  their  situations  with  regard  to  each  other ;  that  some 
perform  revolutions  about  others,  at  known  and  regular  periods, 
and  that  the  motion  of  some  is  direct,  while  that  of  others  is 
retrograde  ;  and  that  many  of  them  have  dark  spots  upon  their 
surface,  and  turn  on  their  axes,  like  the  sun. 

287.  A  remarkable  change  appears  to  be  gradually  taking 
place  in  the  relative  distances  of  the  stars  from  each  other  in 
the  constellation  Hercules.     The  stars  in  this  region  appear  to 
be  spreading  farther  and  farther  apart,  while  those  in  the  oppo- 
site point  of  the  heavens  seem  to  close  nearer  and  nearer  together, 
in  the  same  manner  as  when  walking  through  a  forest,  the  treei 
toward  which  we  advance  appear  to  be  constantly  separating 
while  the  distance  between  those  which  we  leave  behind  is  grr 
dually  contracting. 

by  sight?  How  -vrc  we  to  understand  Moses  as  to  the  time  of  the  creation  of  the  stars? 
285.  What  meant  by  the  "stars"  mentioned  Gen.  i.,  16?  What  proof?  Remark  respit- 
ing the  Scriptures  ?  286.  How  have  the  stars  been  described  hitherto?  What  ia  the. 
tact?  287.  What  example  cited ?  What  astonishing  conclusion ? 


NUMBER,    DISTANCE,    AND   ECONOMY    OF    THE    STARS.    153 

From  this  appearance  it  is  concluded,  that  the  sun,  with  all  its  retinue  of  planetary 
worlds,  is  moving  through  the  regions  of  the  universe,  toward  some  distant  center,  or 
nround  some  wide  circumference  at  the  rate  of  near  thirty  thousand  miles  an  hour ;  and 
that  it  is  therefore  highly  probable,  if  not  absolutely  certain,  that  we  shall  never  occupy 
that  portion  of  absolute  space,  through  which  we  are  at  this  moment  passing,  during 
all  the  succeeding  ages  of  eternity. 

288.  The  direction  of  the  Sun's  motion  is  towards  the  constel- 
lation  of   Hercules ;    R.  A.    259°  ;    Dec.    35°.     This   velocity 
in  space  is  estimated  at  8  miles  per  second,  or  28,000  miles 
per  hour.     His   period  is   about   18,200,000   years  ;   and  the 
arc  of  his  orbit,  over  which  he  has  traveled  since  the  creation 
of  the  world,  amounts  to  only  about  3- oVo-th  Part  of  his  orbit,  or 
about  t  minutes — an  arc  so  small,  compared  with  the  whole,  as 
to  be  hardly  distinguishable  from  a  straight  line. 

With  this  wonderful  fact  in  view,  we  may  no  longer  consider  the  sun  as  fixed  and  sta- 
tionary, but  rather  as  a  vast  and  luminous  planet,  sustaining  the  same  relation  to  some 
central  orb  that  the  primary  planets  sustain  to  him,  or  that  the  secondaries  sustain  to 
their  primaries.  Nor  is  it  necessary  that  the  stupendous  mechanism  of  nature  should  be 
restricted  even  to  these  sublime  proportions.  The  sun's  central  body  may  also  have  its 
orbit,  and  its  center  of  attraction  and  motion,  and  so  on,  till,  as  Dr.  Dick  observes,  we 
come  to  the  great  center  of  all— to  the  THRONE  OF  GOD  ! 

Professor  Madler,  of  Dorpat,  in  Russia,  has  recently  announced  as  a  discovery  that 
the  star  Alcyone,  one  of  the  seven  stars,  is  the  center  around  which  the  sun  and  solar 
Bystem  are  revolving. 

289.  Dr.  Dick,  the  author  of  the  CHRISTIAN  PHILOSOPHER, 
endeavors  to  convey  some  idea  of  the  boundless  extent  of  the 
universe,  by  the  following  sublime  illustration  : — 

"Suppose  that  one  of  the  highest  order  of  intelligences  is 
endowed  with  a  power  of  rapid  motion  superior  to  that  of  light, 
and  with  a  corresponding  degree  of  intellectual  energy  ;  that  he 
has  been  flying  without  intermission,  from  one  province  of  crea- 
tion to  another,  for  six  thousand  years,  and  will  continue  the 
same  rapid  course  for  a  thousand  million  years  to  come,  it  is 
highly  probable,  if  not  absolutely  certain,  that,  at  the  end  of  this 
vast  tour,  he  would  have  advanced  no  farther  than  the  '  sub- 
urbs of  creation/ — and  that  all  the  magnificent  systems  of  mate- 
rial and  intellectual  beings  he  had  surveyed,  during  his  rapid 
flight,  and  for  such  a  length  of  ages,  bear  no  more  proportion  to 
the  whole  empire  of  Omnipotence,  than  the  smallest  grain  of 
sand  does  to  all  the  particles  of  matter  contained  in  ten  thousand 
worlds." 

Were  a  seraph,  in  prosecuting  the  tour  of  creation  in  the  manner  now  stated,  ever  to 
arrive  at  a  limit  beyond  which  no  farther  displays  of  the  Divinity  could  be  perceived,  the 
thought  would  overwhelm  his  faculties  with  unutterable  emotions  ;  he  would  feel  that  he 
had  now,  in  some  measure,  comprehended  all  the  plans  and  operations  of  Omnipotence, 
and  that  no  farther  manifestation  of  the  Divine  glory  remained  to  be  explored.  But  we 
may  rest  assured  that  this  can  never  happen  in  the  case  of  any  created  intelligence. 

288  The  direction  and  velocity  of  the  sun  ?  Period?  Arc  of  orbit  passed  over  sincj 
creation?  How,  then,  should  we  consider  the  sun?  View  of  the  universe ?  Discovery 
of  Professor  Madler  ?  289.  Dr.  Dick's  illustrations  ? 


154  ASTRONOMY. 

290.  There  is,  moreover,  an  argument  derivable  from  the 
laws  of  the  physical  world,  that  seems  to  strengthen,  I  had 
almost  said,  to  confirm,  this  idea  of  the  Infinity  of  the  material 
universe.  It  is  this — If  the  number  of  stars  be  finite,  and 
occupy  only  a  part  of  space,  the  outward  stars  would  be  con- 
tinually attracted  to  those  within,  and  in  time  would  unite  in 
one.  But  if  the  number  be  infinite,  and  they  occupy  an  infinite 
space,  all  parts  would  be  nearly  in  equilibrio,  and  consequently 
each  fixed  star,  being  equally  attracted  in  every  direction,  would 
keep  its  place. 

No  wonder,  then,  that  the  Psalmist  was  so  affected  with  the  idea  of  the  immensity  of 
the  universe,  that  he  seems  almost  afraid  lest  he  should  be  overlooked  amidst  the  immen- 
sity of  beings  that  must  needs  be  under  the  superintendence  of  God ;  nor  that  any  finite 
mortal  should  exclaim,  when  contemplating  the  heavens — "  What  is  man,  that  THOU 
art  mindful  of  him4" 


CHAPTER  XVII. 

FALLING,    OR    SHOOTING    STARS, 

291.  THE  phenomenon  of  shooting  stars,  as  it  is  called,  is  com- 
mon to  all  parts  of  the  earth  ;  but  is  most  frequently  seen  in 
tropical  regions.     The  unerring  aim,  the  startling  velocity,  and 
vivid  brightness  with  which  they  seem  to  dart  athwart  the  sky, 
and  as  suddenly  expire,  excite  our  admiration  ;  and  we  often 
ask,  "  What  can  they  be  ?" 

But  frequent  as  they  are,  this  interesting  phenomenon  is  not 
well  understood.  Some  imagine  that  they  are  occasioned,. by 
electricity,  and  others,  that  they  are  nothing  but  luminous  gas. 
Others  again  have  supposed,  that  some  of  them  are  luminous 
bodies  which  accompany  the  earth  in  its  revolution  around  the 
Bun,  and  that  their  return  to  certain  places  might  be  calculated 
with  as  much  certainty  and  exactness  as  that  of  any  of  the 
comets. 

292.  Dr.  Burney,  of  Gosport,  kept  a  record  of  all  that  he 
observed  in  the  course  of  several  years.     The  number  which  he. 
noticed  in  1819  was  121,  and  in  1820  he  saw  131.     Professor 

290.  What  argument  supposed  to  favor  the  idea  of  a  boundless  universe?  Allusion  tc 
the  Psalmist?  291.  Where  are  shooting  stars  most  common?  Are  they  well  under 
stood  ?  What  theories  stated  ?  292>r  T)r.  Burney's  record?  Professor  Green's  opinion? 
Signior  Baccaria's  opinion,  and  his  reasons  for  it? 


FALLING  OR  SHOOTING  STARS  150 

Green  is  confident  that  a  much  larger  number  are  annually  seen 
in  the  United  States. 

Signior  Baccaria  supposed  they  were  occasioned  by  electricity, 
and  thinks  this  opinion  is  confirmed  by  the  following  observa- 
tions. About  an  hour  after  sunset,  he  and  some  friends,  that 
were  with  him,  observed  a  falling  star  directing  its  course  directly 
toward  them,  and  apparently  growing  larger  and  larger,  but  just 
before  it  reached  them  it  disappeared.  On  vanishing,  their 
faces,  hands,  and  clothes,  with  the  earth  and  all  the  neighboring 
objects,  became  suddenly  illuminated  with  a  diffused  and  lambent 
light.  It  was  attended  with  no  noise.  During  their  surprise  at 
this  appearance,  a  servant  informed  them  that  he  had  seen  a 
light  shine  suddenly  in  the  garden,  and  especially  upon  the 
streams  which  he  was  throwing  to  water  it. 

The  Signior  also  observed  a  quantity  of  electric  matter  collect  about  his  kite,  which 
had  very  much  the  appearance  of  a  falling  star.  Sometimes  he  saw  a  kind  of  hale 
accompanying  the  kite,  as  it  changed  its  place,  leaving  some  glimmering  of  light  in  tho 
place  it  had  quitted. 

293.  Shooting  stars  have  been  supposed  by  those  meteorolo- 
gists who  refer  them  to  electricity  or  luminous  gas,  to  prognos- 
ticate changes  in  the  weather,  such  as  rain,  wind,  &c. ;  and  there 
is,  perhaps,   some  truth  in  this  opinion.     The  duration  of  the 
brilliant  track  which  they  leave  behind  them,  in  their  motion 
through  the  air,  will  probably  be  found  to  be  longer  or  shorter, 
according  as  watery  vapor  abounds  in  the  atmosphere. 

The  notion  that  this  phenomenon  betokens  high  winds,  is  of  great  antiquity.  Virgil, 
in  the  first  book  of  his  Georgics,  expresses  the  same  idea : — 

"  Saepe  etiam  Stellas  vento  impendente  videbis 
Praecipites  ccelo  labi ;  noctisque  per  umbram 
Flammarum  longos  a  tergo  albescere  tractus." 

"  And  oft,  before  tempestuous  winds  arise, 
The  seeming  stars  fall  headlong  from  the  skies, 
And  shooting  through  the  darkness,  gild  the  night 
With  sweeping  glories  and  long  trails  of  light." 

294.  The  number  of  shooting  stars  observed  in  a  single  night, 
though  variable,  is  commonly  very  small.     There  are,  however, 
several  instances  on  record  of  their  falling  in  "  showers  " — when 
every  star  in  the  firmament  seems  loosened  from  its  sphere,  and 
moving  in  lawless  flight  from  one  end  of  the  heavens  to  the 
other. 

As  early  as  the  year  472,  in  the  month  of  November,  a  phe- 
nomenon of  this  kind  took  place  near  Constantinople.  As  Theo- 

293.  What  are  they  supposed  by  some  to  prognosticate  ?  What  other  ancient  notion  ? 
Poetic  quotation?  294.  What  said  of  then-umber  of  shooting  stars?  What  instance1) 
jf  "meteoric  showers"  cited? 


15O  ASTRONOMY. 

phanes  relates,  "  the  sky  appeared  to  be  on  fire,"  with  the  corm*» 
cations  of  the  flying  meteors. 

A  shower  of  stars  exactly  similar  took  place  in  Canada,  between  the  3d  and  4th  of 
July,  1814,  and  another  at  Montreal,  in  November,  1819.  In  all  these  cases,  a  residuum, 
or  black  dust,  was  deposited  upon  the  surface  of  the  waters,  and  upon  the  roofs  of  build- 
ings, and  other  objects.  In  the  year  1810,  "  inflamed  substances,"  it  is  said,  fell  into, 
and  around  lake  Van,  in  Armenia,  which  stained  the  water  of  a  blood  color,  and  cleft 
the  earth  in  various  places.  On  the  5th  of  September,  1819,  a  like  phenomenon  was  seen 
in  Moravia.  History  furnishes  many  more  instances  of  meteoric  showers,  depositing  a 
red  dust  in  some  places,  so  plentiful  as  to  admit  of  chemical  analysis. 

295.  The  commissioner  (Mr.  Andrew  Ellicott),  who  was  sent 
out  by  our  government  to  fix  the  boundary  between  the  Spanish 
possessions  in  North  America  and  the  United  States,  witnessed 
a  -very  extraordinary  flight  of  shooting  stars,  which  filled  the 
whole  atmosphere  from  Cape  Florida  to  the  West  India  Islands. 
This  grand  phenomenon  took  place  the  12th  of  November,  1799, 
and  is  thus  described  : — "  I  was  called  up,"  says  Mr.  Ellicott, 
"  about  3  o'clock  in  the  morning,  to  see  the  shooting  stars,  as 
they  are  called.  The  phenomenon  was  grand  and  awful.  The 
whole  heavens  appeared  as  if  illuminated  with  sky-rockets, 
which  disappeared  only  by  the  light  of  the  sun,  after  daybreak. 
The  meteors,  which  at  any  one  instant  of  time  appeared  as 
numerous  as  the  stars,  flew  in  all  possible  directions  except  from 
the  earth,  toward  which  they  all  inclined  more  or  less,  and  some 
of  them  descended  perpendicularly  over  the  vessel  we  were  in,  so 
that  I  was  in  constant  expectation  of  their  falling  on  us." 

Mr.  Ellicott  further  states  that  his  thermometer,  which  had  been  at  80°  Fahr.  for  the  four 
days  preceding,  fell  to  56°  about  4  o'clock,  A.  M.,  and  that  nearly  at  the  same  time,  the 
wind  changed  from  the  south  to  the  northwest,  from  whence  it  blew  with  great  violence 
for  three  days  without  intermission. 

These  same  appearances  were  observed  the  same  night  at  Santa  Pe  de  Bogota,  Cu- 
mana,  Quito,  and  Peru,  in  South  America  ;  and  as  far  north  as  Labrador  and  Greenland, 
extending  to  Weimar  in  Germany,  being  thus  visible  over  an  extent  on  the  globe  of  64* 
of  latitude,  and  94°  of  longitude. 

The  celebrated  Humboldt,  accompanied  by  M.  Bompland, 
then  in  S.  America,  thus  speaks  of  the  phenomenon  : — "  Toward 
the  morning  of  the  13th  of  November,  1799,  we  witnessed  a 
most  extraordinary  scene  of  shooting  meteors.  Thousands  of 
bolides,  and  falling  stars  succeeded  each  other  during  four  hours. 
Their  direction  was  very  regular  from  north  to  south.  From 
the  beginning  of  the  phenomenon  there  was  not  a  space  in  the 
firmament,  equal  in  extent  to  three  diameters  of  the  moon, 
which  was  not  filled  every  instant  with  bolides  or  falling  stars. 
All  the  meteors  left  luminous  traces,  or  phosphorescent  bands 
behind  them,  which  lasted  seven  or  eight  seconds." 

295.  What  phenomenon  described  by  Mr.  Ellicott  ?  When  and  where  ?  EtiVf •  on  hie 
thermometer  ?  Where  else  observed,  and  by  whom? 


FALLING    OR    SHOOTING    STARS  157 

Thy  phenomenon  was  witnessed  by  the  Capuchin  missionary  at  San  Fernando  do 
Afiur*,  a  village  situated  in  lat.  7°  53'  12",  amidst  the  savannahs  of  the  province  of 
Varinas;  by  the  Franciscan  monks  stationed  near  the  cataracts  of  the  Oronoco,  and  at 
Marca,  on  the  banks  of  the  Rio  Negro,  lat.  2°  40",  long.  70°  21',  and  in  the  west  of  Bra2.il, 
as  far  as  the  equator  itself;  and  also  at  the  city  of  Porto  Cabello,  lat.  10°  6'  52",  in  French 
Guiana,  Popayan,  Quito,  and  Peru.  It  is  somewhat  surprising  that  the  same  appearances, 
)bderved  in  places  so  widely  separated,  amid  the  vast  and  lonely  deserts  of  South 
Vmerica,  should  have  been  seen,  the  same  night,  in  the  Ijnited  States,  in  Labrador,  in 
Greenland,  and  at  Itterstadt,  near  Weimar,  in  Germany ! 

296.  We  are  told  that  thirty  years  before,  at  the  city  of 
Quito,  "there  was  seen  in  one  part  of  the  sky,  above  the  volcano 
of  Cayamburo,  so  great  a  number  of  falling  stars,  that  the  moun- 
tain was  thought  to  be  in  flames.     This  singular  sight  lasted 
more  than  an  hour.     The  people  assembled  in  the  plain  of  Exida, 
where  a  nmgnificent  view  presents  itself  of  the  highest  summits 
of  the  Cordilleras.     A  procession  was  already  on  the  point  of 
setting  out  from  the  convent  of  St.  Francis,  when  it  was  per 
ceived  that  the  blaze  on  the  horizon  was  caused  by  fiery  meteors, 
which  ran  along  the  sky  in  all  directions,  at  the  altitude  of  12 
or  13  degrees." 

297.  But  the  most  sublime  phenomenon  of  shooting  stars,  of 
which  the  world  has  furnished  any  record,  was  witnessed  through- 
out the  United  States  on  the  morning  of  the  13th  of  November, 
1833.     The  entire  extent  of  this  astonishing  exhibition  has  not 
been  precisely  ascertained,  but  it  covered  no  inconsiderable  por- 
tion of  the  earth's  surface.     It  has  been  traced  from  the  longi- 
tude of  61°,  in  the  Atlantic  ocean,  to  longitude  100°  in  Central 
Mexico,  and  from  the  North  American  lakes  to  the  West  Indies. 
It  was  not  seen,  however,  anywhere  in  Europe,  nor  in  South 
America,  nor  in  any  part  of  the  Pacific  Ocean  yet  heard  from. 

Everywhere,  within  the  limits  above  mentioned,  the  first 
appearance  was  that  of  fireworks  of  the  most  imposing  grandeur, 
covering  the  entire  vault  of  heaven  with  myriads  of  fire-balls, 
resembling  sky-rockets/  Their  coruscations  were  bright,  gleam- 
ing and  incessant,  and  they  fell  thick  as  the  flakes  in  the  early 
snows  of  December.  (See  cut  on  the  next  page.) 

To  the  splendors  of  this  celestial  exhibition,  the  most  brilliant  sky-rockets  and  fire- 
works of  art  bear  less  relation  than  the  twinkling  of  the  most  tiny  star  to  the  broad 
glare  of  the  sun.  The  whole  heavens  seemed  in  motion,  and  suggested  to  some  the  awful 
grandeur  of  the  image  employed  in  the  apocalypse,  upon  the  opening  of  the  sixth  seal, 
when  "  the  stars  of  heaven  fell  unto  the  earth,  even  as  a  fig-tree  casteth  her  untimely 
figs,  when  she  is  shaken  of  a  mighty  wind." 

298.  One  of  the  most  remarkable  circumstances  attending 
his  display  was,  that  the  meteors  all  seemed  to  emanate  from 

296.  What  other  similar  phenomenon  cited  ?  297.  What  still  more  sublime  spectacle/ 
to  extent?  Its  appearance  ? 


Ib8 


ASTRONOMY. 


one  and  the  same  point,  a  little  southeast  of  the  zenith.  Follow- 
ing the  arch  of  the  sky,  they  ran  along  with  immense  velocity, 
describing,  in  some  instances,  an  arc  of  30°  or  40°  in  a  few 


METEORIC  SHOWBK  OF  NOVEMBER,  1S33. 

seconds.  On  more  attentive  inspection  it  was  seen,  that  the 
meteors  exhibited  three  distinct  varieties  ;  the  first,  consisting 
of  phosphoric  lines,  apparently  described  by  a  point ;  the  second, 
of  large  fire-balls,  that  at  intervals  darted  along  the  sky,  leaving 
luminous  trains,  which  occasionally  remained  in  view  for  a  num- 
ber of  minutes,  and,  in  some  cases,  for  half  an  hour  or  more  ; 
the  third,  of  undefined  luminous  bodies,  which  remained  nearly 
stationary  in  the  heavens  for  a  long  time. 

Those  of  the  first  variety  were  the  most  numerous,  and  resembled  a  shower  of  fiery 
snow  driven  with  inconceivable  velocity  to  the  north  of  west.  The  second  kind  appeared 
more  \\kefalling  stars — a  spectacle  which  was  contemplated  by  the  more  unenlightened 
beholders  with  great  amazement  and  terror.  The  trains  which  they  left  were  commonly 
white,  but  sometimes  were  tinged  with  various  prismatic  colors,  of  great  beauty. 

299.  These  fire-balls  were  occasionally  of  enormous  size.  Dr. 
Smith,  of  North  Carolina,  describes  one  which  appeared  larger 
than  the  full  moon  rising.  "  I  was,"  says  he,  "  startled  by  the 

298  What  remarkable  circumstance  attended  this  phenomenon?  Variety  of  meteors? 
209.  What  said  of  the  fireballs  seen?  Of  their  size? 


FALLING  OR  SHOOTING  STARS. 


159 


A   LARGK  METEOR. 


splendid  light  in  which  the  surrounding  scene  was  exhibited,  ren- 
dering even  small  objects  quite  visible." 

The  same  ball,  or  a  similar  one, 
seen  at  New  Haven,  passed  off  in  a 
northwest  direction,  and  exploded  a 
little  northward  of  the  star  Capella, 
leaving,  just  behind  the  place  of 
explosion,  a  train  of  peculiar  beauty. 
The  line  of  direction  was  at  first 
nearly  straight ;  but  it  soon  began  to 
contract  in  length,  to  dilate  in  breadth, 
and  to  assume  the  figure  of  a  serpent 
SCROLLING  itself  up,  until  it  appeared 
like  a  luminous  cloud  of  vapor,  float- 
ing gracefully  in  the  air,  where  it 
remained  ia  full  view  for  several 
minutes. 

If  this  body  were  at  the  distance  of 
110  miles  from  the  observer,  it  must 
have  had  a  diameter  of  one  mile ;  if 
at  the  distance  of  11  miles,  its  diame- 
ter was  528  feet ;  and  if  only  one  mile 

off,  it  must  have  been  48  feet  in  diameter.    These  tonsiderations  leave  no  doubt  that 
many  of  the  meteors  were  bodies  of  large  size. 

300.  Of  the  third  variety  of  meteors,  the  following  are  remark- 
able examples  : — At  Poland,  Ohio,  a  luminous  body  was  dis- 
tinctly visible  in  the  northeast  for  more  than  an  hour.     It  was 
very  brilliant,  in  the  form  of  a  pruning-hook,  and   apparently 
twenty   feet   long,    and   eighteen   inches  broad.     It   gradually 
settled  toward  the  horizon,  until  it  disappeared. 

At  Niagara  Falls,  a  large  luminous  body,  shaped  like  a  square  table,  was  seen  near 
the  zenith,  remaining  for  some  time  almost  stationary,  emitting  large  streams  of  light. 

301.  The  point  from  which  the  meteors  seemed  to  emanate, 
was  observed,  by  those  who  fixed  its  position  among  the  stars, 
to  be  in  constellation  Leo  ;  and,  according  to  their  concurrent 
testimony,  this  RADIANT  POINT  was  stationary  among  the  stars, 
during  the  whole  period  of  observation  ;  that  is,  it  did  not  move 
along  with  the  earth,  in  its  diurnal  revolution  eastward,  but 
accompanied  the  stars  in  their  apparent  progress  westward. 

A  remarkable  change  ofweatfier,  from  warm  to  cold,  accompanied  the  meteoric 
shower,  or  immediately  followed  it.  In  all  parts  of  the  United  States,  this  change  was 
remarkable  for  its  suddenness  and  intensity.  In  many  places,  the  day  preceding  had 
been  unusually  warm  for  the  season,  but,  before  the  next  morning,  a  severe  frost  ensued, 
unparalleled  for  the  tune  of  year. 

302.  In  attempting  to  explain  these  mysterious  phenomena,  it 
is  argued,  in  the  first  place,  that  the  meteors  had  their  origin 
beyond  the  limits  of  our  atmosphere  ;  that  they  of  course  did  not 
belong  to  this  earth,  but  to  the  regions  of  space  exterior  to  it 

800.  What  other  variety  of  meteors  described  ?  Where  ?  801.  Point  from  which 
.hey  seemed  to  emanate  ?  What  change  of  weather  follc  red  ?  802.  What  fact  asserted 
firf  to  the  dwtanoe  from  which  those  meteors  came  Professor  Olmsted's  estimate  ot 
dibt  ince  ? 


i60  ASTRONOMY. 

The  reason  on  which  the  conclusion  is  founded  is  this  :— All  bodies  near  the  eartL 
including  the  atmosphere  itself,  have  a  common  motion  with  the  earth  around  its  axis 
from  west  to  east;  but  the  radiant  point,  that  indicated  the  source  from  which  the 
meteors  emanated,  followed  the  course  of  the  stars  from  east  to  west ;  therefore,  it  was 
Independent  of  the  earth's  rotation,  and  consequently,  at  a  great  distance  from  it,  ana 
beyond  the  limits  of  the  atmosphere.  The  height  of  the  meteoric  cloud,  or  radiant  point, 
above  the  earth's  surface,  was,  according  to  the  mean  average  of  Professor  Ounsted'a 
observations,  not  less  than  2238  miles. 

303.  That  the  meteorsVere  constituted  of  very  light,  combus- 
tible materials,  seems  to  be  evident,  from  their  exhibiting  the 
actual  phenomena  of  combustion,  they  being  consumed,  or  con- 
verted into  smoke,  with-  intense  light  ;  and  the  extreme  tenuity 
of  the  substance  composing  them  is  inferred  from  the  fact  that 
they  were  stopped  by  the  resistance  of  the  air.     Had  their  quan- 
tity of  matter  been  considerable,  with  so  prodigious  a  velocity, 
they  would  have  had  sufficient  momentum  to  dash   them  upon 
the  earth  ;  where  the  most  disastrous  consequences  might  have 
followed. 

The  momentum  of  even  light  bodies  of  such  size,  and  in  such  numbers,  traversing  the 
atmosphere  with  such  astonishing  velocity,  must  have  produced  extensive  derangements 
in  the  atmospheric  equilibrium.  Cold  air  from  the  upper  regions  would  be  brought  down 
to  the  earth;  the  portions  of  air  incumbent  over  districts  of  country  remote  from  each 
other,  being  mutually  displaced,  would  exchange  places,  the  air  of  the  warm  latitudes  be 
transferred  to  colder,  and  that  of  cold  latitudes  to  warmer  regions. 

304.  Various  hypotheses  have  been  proposed  to  account  for  this 
wonderful  phenomena.     The  agent  which  most  readily  suggests 
itself  in  this,  and  in  many  other  unexplained  natural  appearances, 
is  electricity.     But  no  known  properties  of  electricity  are  adequate 
to  account  for  the  production  of  the  meteors,  for  their  motions,  or 
for  the  trains  which  they,  in  many  instances,  left  behind  them. 
Others,  again,  have  referred  their  proximate  cause  to  magnetism. 
and  to  phosphureted  hydrogen  ;  both  of  which,  however,  seem  to 
be  utterly  insufficient,  so  far  as  their  properties  are  known,  to 
account  for  so  unusual  a  phenomenon. 

305.  Professor  Olmsted,  of  Yale  College,  who  has  taken  much 
pains  to  collect  facts,  and  to  establish  a  permanent  theory  for 
the  periodical  recurrence  of  such  phenomena,  came  to  the  con- 
clusion, that — 

The  meteors  of  November  13th,  1833,  emanated  from  a  nebulous 
body,  which  was  then  pursuing  its  way  along  with  the  earth  around 
the  sun  ;  that  this  body  continues  to  revolve  around  the,  sun,  in  an 
elliptical  orbit — but  little  inclined  to  the  plane  of  the  ecliptic,  ana 
having  its  aphelion  near  the  orbit  of  the  earth ;  and  finally,  thai 

803.  Supposed  composition  of  these  meteors?  Why?  804.  Hypotheses  for  explain* 
fng  phenomenon?  Are  they  satisfactory?  805.  Professor  Olmsted's  conclusion; 


FALLING  OR  SHOOTING  STARS.  161 

tJie,  body  has  a  period  of  nearly  six  months,  and  that  its  perihelion 
is  a  Hi  tie  below  the  orbit  of  Mercury.* 

This  theory  at  least  accommodates  itself  to  the  remarkable  fact,  that  almost  all  the 
phenomena  of  this  description,  which  are  known  to  have  happened,  have  occurred  in  the 
two  opposite  months  of  April  and  November.  A  similar  exhibition  of  meteors  to  that  of 
November,  1833,  was  observed  on  the  same  day  of  the  week,  April  20th,  1803,  at  Kich- 
mond,  Virginia ;  Stockbridge,  Massachusetts  ;  and  at  Halifax,  in  British  America.  Another 
WAS  witnessed  in  the  autumn  of  1818,  in  the  North  Sea,  when,  in  the  language  of  the 
observers,  "  all  the  surrounding  atmosphere  was  enveloped  in  one  expansive  sea  of  fire, 
exhibiting  the  appearance  of  another  Moscow,  in  flames." 

*  After  the  first  edition  of  this  work  went  to  press,  the  author  was  politely  fur- 
nished, by  Professor  Olmsted,  with  the  following  communication. 

"  I  am  happy  to  hear  that  you  propose  to  stereotype  your  '  Geography  of  the  Heavens, 
it  has  done  much,  I  believe,  to  diffuse  a  popular  knowledge  of  astronomy,  and  I  am  pleased 
that  your  efforts  are  rewarded  by  an  extended  patronage. 

"Were  I  now  to  express  my  views  on  the  subject  (Meteoric  /Showers)  in  as  condensed 
a  form  as  possible,  I  should  state  there,  in  some  such  terms  as  the  following :  The  meteoric 
showers  which  have  occurred  for  several  years  past  on  or  about  the  13th  of  Novemberv 
are  characterized  by  four  peculiarities,  which  distinguish  them  from  ordinary  shooting 
stars.  First,  they  are  far  more  numerous  than  common,  and  are  larger  and  brighter. 
Secondly,  they  are  in  much  greater  proportion  than  usual,  accompanied  by  luminous 
trains.  Thirdly,  thsy  mostly  appear  to  radiate  from  a  common  center ;  that  is,  were 
their  paths  in  the  heavens  traced  backward,  they  would  meet  in  the  same  part  of  the 
heavens :  this  point  has  for  three  years  past,  at  least,  been  situated  in  the  constellation 
Leo.  Fourthly,  the  greatest  display  is  everywhere  at  nearly  the  same  time  of  night, 
namely,  from  three  to  four  o'clock — a  time  about  half-way  from  midnight  to  sunrise.  The 
meteors  are  inferred  to  consist  of  combustible  matter,  because  they  are  seen  to  take  firo 
and  burn  in  the  atmosphere.  They  are  known  to  be  very  light,  because,  although  they 
fall  toward  the  earth  with  immense  velocity,  few,  if  any,  ever  reach  the  earth,  but  are 
arrested  by  the  air,  like  a  wad  fired  from  a  piece  of  artillery.  Some  of  them  are  inferred 
to  be  bodies  of  comparatively  great  size,  amounting  in  diameter  to  several  hundred  feet, 
at  least,  because  they  are  seen  under  so  large  an  angle,  while  they  are  at  a  great  distance 
from  the  spectator.  Innumerable  small  bodies,  thus  consisting  of  extremely  light,  thin, 
combustible  matter,  existing  together  in  space  far  beyond  the  limits  of  the  atmosphere, 
are  believed  to  compose  a  body  of  immense  extent,  which  has  been  called  '  the  nebulous 
body.'  Only  the  skirts  or  extreme  portions  of  this  are  brought  down  to  the  earth,  while 
the  entire  extent  occupies  many  thousands,  and  perhaps  several  millions  of  miles.  This 
nebulous  body  is  inferred  to  have  a  revolution  around  the  sun,  as  well  as  the  earth,  and 
to  come  very  near  to  the  latter  about  the  13th  of  November  each  year.  This  annual 
meeting  every  year,  for  several  years  in  succession,  could  not  take  place  unless  the 
periodic,  time  of  the  nebulous  body  is  either  nearly  a  year,  or  half  a  year.  Various  rea- 
sons have  induced  the  belief  that  half  a  year  is  the  true  period ;  but  this  point  is  con- 
sidered somewhat  doubtful.  The  zodiacal  light,  a  faint  light  that  appears  at  different 
seasons  of  the  year,  either  immediately  preceding  the  morning  or  following  the  evening 
twi!:j;ht,  ascending  from  the  sun  in  a  triangular  form,  is,  with  some  degree  of  probability, 
tho  jght  to  be  the  nebular  body  itself,  although  the  existence  of  such  a  body,  revolving 
in  the  solar  system,  was  inferred  to  be  the  cause  of  the  meteoric  showt-s,  before  any 
connection  of  it  with  the  zodiacal  light  was  even  thought  of." 

W?tti  what  remarkable  fact  docs  uis  theory  accord  ?    Substance  of  letter  from  Professor 
Olmsted? 


162  ASTRONOMY. 

306.  Exactly  one  year  previous  to  the  great  phenomenon  of 
1833,  namely,  on  the  12th  of  November,  1832,  a  similar  moteoric 
display  was  seen  near  Mocha,  on  the  Red  Sea,  by  Capt.  Ham- 
mond and  crew  of  the  ship  Restitution. 

A  gentleman  in  South  Carolina  thus  describes  the  effect  of  the  phenomenon  of  1833, 
ipon  his  ignorant  blacks :  "  I  was  suddenly  awakened  by  the  most  distressing  cries  tha^ 
ever  fell  on  my  ears.  Shrieks  of  horror,  and  cries  of  mercy,  I  could  hear  from  most  or 
the  negroes  of  three  plantations,  amounting  in  all  to  about  six  or  eight  hundred.  While 
earnestly  listening  for  the  cause,  I  heard  a  faint  noise  near  the  door  calling  my  name  ; 
I  arose,  and  taking  my  sword,  stood  at  the  door.  At  this  moment,  I  heard  the  same 
voice  still  beseeching  me  to  rise,  and  saying,  '0,  my  God,  the  world  is  on  fire  !'  I  then 
opened  the  door,  and  it  is  difficult  to  say  which  excited  me  most — the  awfulness  of  the 
scene,  or  the  distressed  cries  of  the  negroes ;  upward  of  one  hundred  lay  prostrate  on  the 
ground — some  speechless,  and  some  with  the  bitterest  cries,  but  most  with  their  hands 
raised,  imploring  God  to  save  the  world  and  them.  The  scene  was  truly  awful ;  foi 
never  did  rain  fall  much  thicker,  than  the  meteora  fell  toward  the  earth ;  east,  wist, 
north,  and  south,  it  was  the  same  !" 

806.  What  similar  meteoric  shower  referred  to  ?  Description  of  that  of  November 
1333,  and  its  effects  upon  certain  persons  ? 


PART    II. 
THE    SOLAR    SYSTEM 


CHAPTER  I. 

GENERAL     PHENOMENA      OF     THE     SOLAR     SYSTEM, 
HISTORY,    &o. 

307.  OUR  attention  has  hitherto  been  directed  to  those  bodies 
which  we  see  scattered  everywhere  throughout  the  whole  celes- 
tial concave.     These  bodies,  as  has  been  shown,  twinkle  with  a 
reddish  and  variable  light,  and  appear  to  have  always  the  same 
position  with  regard  to  each  other.     We  know  that  their  num- 
ber is  very  great,  and  that  their  distance  from  us  is  immeasur- 
able. 

We  are  also  acquainted  with  their  comparative  brightness,  and  their  situation.  In  a 
word,  we  have  before  us  their  few  visible  appearances,  to  which  our  knowledge  of  them 
is  well-nigh  limited  ;  almost  all  our  reasonings  in  regard  to  them  being  founded  on  con^ 
parattvely  few  and  uncertain  analogies.  Accordingly,  our  chief  business  thus  far  has 
been  to  detail  their  number,  to  describe  their  brightness  and  positions,  and  to  give  the 
name?  by  which  they  have  been  designated. 

308.  There  now  remain  to  be  considered  certain  other  celes- 
tial bodies,  all  of  which,  from  their  remarkable  appearance  and 
changes,  and  some  of  them  from  their  intimate  connection  witli 
the  comfort,  convenience,  and  even  existence  of  man,  must  have 
always  attracted  especial  observation,  and  been  objects  of  the 
most  intense  contemplation  and  the  deepest  interest.     Most  of 
these  bodies  are  situated  within  the  Uinits  of  the  Zodiac.     The 
most  important  of  them  are,  the  SUN,  so  superior  to  all  the 
heavenly  bodies  for  its  apparent  magnitude,  for  the  light  and 
heat  which  it  imparts,  for  the  marked  effects  of  its  changes  of 
position  with  regard  to  the  Earth  ;  and  the  MOON,  so  conspicu- 
ous among  the  bodies  which  give  light  by  night,  and  from  her 

807.  Subject  of  Part  II.?  Of  our  investigations  hitherto?  How  distinguished  ?  IheJi 
number,  distance,  &c.  ?  What  has  been  our  chief  business  thus  far?  308.  What  o<nv 
remains  to  be  considered?  How  situated?  Which  the  most  important  of  them? 


1 64  ASTRONOMY. 

soft  and  silvery  brightness,  so  pleasing  to  behold  ;  remarkable 
not  only  for  changes  of  position,  but  for  the  varied  phases  or 
appearances  which  she  presents,  as  she  waxes  from  her  crescent 
form  through  all  her  different  stages  of  increase  to  a  full  orb, 
and  wanes  back  again  to  her  former  diminished  figure. 

309.  The  partial  or  total  obscuration  of  these  two  bodies, 
which  sometimes  occurs,  darkness  taking  place  even  at  mid-day, 
and  the  face  of  night,  before  lighted  up  by  the  Moon's  beams, 
being  suddenly  shaded  by  their  absence,  have  always  been  among 
the  most  striking  astronomical  phenomena,  and  so  powerful  in 
their  influence  upon  the  beholders,  as  to  fill  them  with  perplexity 
and  fear. 

310.  If  we  observe   these  two  bodies,  we   shall   find  that, 
besides  their  apparent  diurnal  motion,  across  the  heavens,  they 
exhibit  other  phenomena,  which  must  be  the  effect  of  motion. 
The  Sun  during  one  part  of  the  year  will  be  seen  to  rise  every 
day  farther  and  farther  toward  the  north,  to  continue  longer  and 
longer  above  the  horizon,  to  be  more  and  more  elevated  at  mid- 
day, until  he  arrives  at  a  certain  limit ;  and  then,  during  the 
other  part,  the  order  is  entirely  reversed. 

311.  Again  ;  if  the  Sun's  motions  be  attentively  observed,  he 
will  be  found  to  have  another  motion,  opposite  to  his  apparent 
diurnal  motion  from  east  to  west.     This  may  be  perceived  dis- 
tinctly, if  we  notice,  on  any  clear  evening,  any  bright  star  which 
is  first  visible  after  sunset,  near  the  place  where  he  sunk  below 
the  horizon.     The  following  evening,  the  star  will  not  be  visible 
on  account  of  the  approach  of  the  Sun,  and  all  the  stars  on  the 
east  of  it  will  be  successively  eclipsed  by  his  rays,  until  he  shall 
have  made   a   complete   apparent  revolution  in   the   heavens. 
These  are  the  most  obvious  phenomena  exhibited  by  these  two 
bodies. 

312.  The  Moon  sometimes  is  not  seen  at  all ;  and  then,  when 
she  first  becomes  visible,  appears  in  the  west,  not  far  from  the 
setting  Sun,  with  a  slender  crescent  form  ;    every  night  she 
appears  at  a  greater  distance  from  the  setting  Sun,  increasing  in 
size,  until  at  length  she  is  found  in  the  east,  just  as  the  Sun  is 
sinking  below  the  horizon  in  the  west. 

313.  There  are  also  situated  within  the  limits  of  the  Zodia< 
certain  other  bodies,  which,  at  first  view  and  on  a  superficial 
examination,  are  scarcely  distinguishable  from  the  fixed  stars. 

809.  ^Vhat  said  of  their  obscuration  ?  810.  Of  their  motions  ?  811.  Has  the  Srn 
an  apparent  eastward  motion  ?  312.  What  said  of  the  Moon's  motions  and  phase*.  ( 
£18.  What  other  bodies  and  their  motions  ?  What  called,  and  why  ? 


PHENOMENA    OF    THE    SOLAR    SYSTEM.  165 

Bat,  observed  more  attentively,  they  will  be  seen  to  shine  with 
a  milder  and  steadier  light,  and,  besides  being  carried  round 
with  the  stars,  in  the  apparent  revolution  of  the  great  celestial 
concave,  they  will  seem  to  change  their  places  in  the  concave 
itself.  Sometimes  they  are  stationary  ;  sometimes  they  appear 
to  be  moving  from  west  to  east,  and  sometimes  to  be  going  back 
again  from  east  to  west ;  being  seen  at  sunset  sometimes  in  the 
east,  and  sometimes  in  the  west,  and  always  apparently  changing 
their  position  with  regard  to  the  earth,  each  other,  and  the 
other  heavenly  bodies.  From  their  wandering,  as  it  were,  ic 
this  manner  through  the  heavens,  they  were  called  by  the  Greeks 
TTkavrjrai,  planets,  which  signifies  wanderers. 

314.  There  also  sometimes  appear  in  the  heavens,  bodies  of  a 
very  extraordinary  aspect,  which  continue  visible  for  a  considera- 
ble period,  and  then  disappear  from  our  view  ;  and  nothing  more 
is  seen  of  them,  it  may  be,  for  years,  when  they  again  present 
themselves,  and  take  their  place  among  the  bodies  of  the  celes- 
tial sphere.     They  are  distinguished  from  the  planets  by  a  dull 
and  cloudy  appearance,    and  by  a   train   of  light.     As   they 
approach  the  sun,  however,  their  faint  and  nebulous  light  becomes 
more  and  more  brilliant,   and  their  train  increases  in  length 
until  they  arrive  at  their  nearest  point  of  approximation,  when 
they  shine  with  their  greatest  brilliancy.     As  they  recede  from 
the  Sun,  they  gradually  lose  their  splendor,  resume  their  faint 
and  nebulous  appearance,  and  their  train  diminishes,  until  they 
entirely  disappear.     They   have   no   well-defined   figure  ;    they 
seem  to  move  in  every  possible  direction,  and  are  found  in  every 
part  of  the  heavens.     From  their  train  they  were  called  by  the 
Greeks    Kourjrai,    wmets,    which    signifies    bearded,    or   having 
long  hair. 

The  causes  of  these  various  phenomena  must  have  early  constituted  a  very  natural 
subject  of  inquiry.  Accordingly,  we  shall  find,  if  we  examine  the  history  of  the  science, 
that  in  very  early  times  there  were  many  speculations  upon  this  subject,  and  that  differ- 
ent theories  were  adopted  to  account  for  these  celestial  appearances. 

315.  The  Egyptians,  Chaldeans,  Indians,  and  Chinese,  early 
possessed  many  astronomical  facts,  many  observations  of  impor- 
tant phenomena,  and  many  rules  and  methods  of  astronomical 
calculation  ;  and  it  has  been  supposed,  that  they  had  the  ruins 
of  a  great  system  of  astronomical  science,  which  in  the  earliest 
ages  of  the  world  had  been  carried  to  a  great  degree  of  perfec- 
tion, and  that  while  the  principles  and  explanations  of  the  phe- 

814.  Any  other  bodies  described?  How  distinguished?  What  called,  and  why  ?  Is  it 
probable  that  these  phenomena  were  early  observed?  315.  What  said  of  the  Egyptians 
Uhaldeans,  <fec.?  Of  the  Chinese  in  particular?  Of  the  Indians  and  Chaldeans'/ 


166  ASTRONOMY. 

nomena  were  lost,  the  isolated,  unconnected  facts,  rules  of  calcu- 
lation, and  phenomena  themselves,  remained. 

Thus,  the  Chinese,  who,  it  is  generally  agreed,  possess  the  oldest  authentic  observa- 
tions on  record,  have  recorded  in  their  annals,  a  conjunction  of  five  planets  at  the  same 
time,  which  happened  2461  years  before  Christ,  or  100  years  before  the  flood.  By  mathe» 
matical  calculation,  it  is  ascertained  that  this  conjunction  really  occurred  at  that  time 
The  first  observation  of  a  solar  eclipse  of  which  the  worhl  has  any  knowledge,  was  made 
by  the  Chinese,  2128  years  before  Christ,  or  220  'years  after  the  deluge.  It  seems,  also, 
that  the  Chinese  understood  the  method  of  calculating  eclipses ;  for,  it  is  said,  that  the 
emperor  was  so  irritated  against  the  great  officers  of  state  for  neglecting  to  predict  tho 
eclipse,  that  he  caused  them  to  be  put  to  death.  The  Chinese  have,  from  time  imme- 
morial, considered  Solar  Eclipses  and  conjunctions  of  the  planets,  as  prognostics  of 
importance  to  the  Empire,  and  they  have  been  predicted  as  a  matter  of  state  policy. 

The  astronomical  epoch  of  the  Chinese,  according  to  Bailly,  commenced  with  Pohi, 
their  first  emperor,  who  flourished  2952  years  before  the  Christian  era,  or  about  350 
years  before  the  deluge.  If  it  be  asked  how  the  knowledge  of  this  antediluvian  astrono- 
my was  preserved  and  transmitted,  it  is  said  that  the  columns  on  which  it  was  registered 
have  survived  the  deluge,  and  that  those  of  Egypt  are  only  copies  which  have  become 
originals,  now  that  the  others  have  been  forgotten.  The  Indians,  also,  profess  to  have 
many  celestial  observations  of  a  very  early  date.  The  Chaldeans  have  been  justly  cele- 
brated in  all  ages  for  their  astronomical  observations.  When  Alexander  took  Babylon, 
his  preceptor,  Callisthenes,  found  a  series  of  Chaldean  observations,  made  in  that  city, 
and  extending  back,  with  little  interruption,  through  a  period  of  1903  years  preceding 
that  event.  This  would  carry  us  back  to  at  least  2234  years  before  the  birth  of  Christ, 
or  to  about  the  time  of  the  dispersion  of  mankind  by  the  confusion  of  tongues. 

316.  The  Greeks,  in  all  probability,   derived  many  notions 
in  regard  to  this  science,  and  many  facts  and  observations,  from 
Egypt,  the  great  fountain  of  ancient  learning  and  wisdom,  and 
many  were  the  speculations  and  hypotheses  of  their  philosophers. 
The  first  of  the  Greek  philosophers  who  taught  Astronomy  was 
Thales,  of  Miletus.     He  flourished  about  640  years  before  the 
Christian    era.       Then    followed    Anaximander,    Anaximenes 
Anaxagoras,  Pythagoras,  Plato. 

Some  of  the  doctrines  maintained  by  these  phuosophers  were,  that  the  Earth  wah 
round,  thav  it  had  two  motions,  a  diurnal  motion  on  its  axis,  and  an  annual  motion 
around  the  Sun,  that  the  Sun  was  a  globe  of  fire,  that  the  Moon  received  her  light  from 
the  Sun,  that  she  was  habitable,  contained  mountains,  seas,  Ac. :  that  her  eclipses  wer, 
caused  by  the  Earth's  shadow,  that  the  planets  were  not  designed  merely  to  adorn  our 
heavens,  that  they  were  worlds  of  themselves,  and  that  the  fixed  stars  were  centers  of 
distant  systems.  Some  of  them,  however,  maintained  that  the  Earth  was  flat,  and  others 
that,  though  round,  it  was  at  rest  in  the  center  of  the  universe. 

317.  When  that  distinguished  school  of  philosophy  was  estab- 
lished at  Alexandria,  in  Egypt,  by  the  munificence  of  the  sove- 
reigns to  whom  that  portion  of  Alexander's  empire  had  fallen, 
astronomy  recived  a  new  impulse.     It  was  now,  in  the  second 
century  after  Christ,  that  the  first  complete  system  or  treatise 
of  astronomy  of  which  we   have  any  knowledge,  was  formed. 
All   before   had   been  unconnected  and  incomplete.     Ptolemy, 
with  the  opinions  of  all  antiquity,  and  of  all  the  philosophers 

816.  Of  the  Greeks?    Who  first  taught  astronomy  among  them.?    Date?    Who  n»xt? 
State  some  of  their  doctrines?       317.  What  record  of  this  science?    What  of 
and  his  works  ? 


PHENOMENA    OF    THE    SOLAR    SYSTEM.  167 

who  had  preceded  him,  spread  out  before  him,  composed  a  work 
m  thirteen  books,  called  the  Meya/U;  Svvrat;^ ,  or  Great  System. 

318.  Rejecting  the  doctrine  of  Pythagoras,  who  taught  that 
the  Sun  was  the  center  of  the  universe,  and  that  the  Earth  had 
a  diurnal  motion  on  its  axis  and  an  annual  motion  around  the 
Sun,  as  contrary  to  the  evidence  of  the  senses,  Ptolemy  endea- 
vored to  account  for  the  celestial  phenomena,  by  supposing  the 
Earth  to   be  the  center  of  the  universe,  and  all  the  heavenly 
bodies  to  revolve  around  it. 

He  seems  to  have  entertained  an  idea,  in  regard  to  the  supposition,  that  the  Earth 
revolved  on  its  axis,  similar  to  one  which  some  entertain  even  at  the  present  day.  "  If," 
says  he,  "  there  were  any  motion  of  the  Earth  common  to  it  and  all  other  heavenly 
bodies,  it  would  certainly  precede  them  all  by  the  excess  of  its  mass  being  so  great;  and 
animals  and  a  certain  portion  of  heavy  bodies  would  be  left  behind,  riding  upon  the  air, 
and  the  earth  itself  would  very  soon  be  completely  carried  out  of  the  heavens." 

319.  In  explaining  the  celestial  phenomena,  however,  upon 
his  hypothesis,  he  met  with  a  difficulty  in  the  apparently  station- 
ary attitude  and  retrograde  motions  which  he  saw  the  planets 
sometimes   have.     To  explain  this,  however,  he  supposed  the 
planets  to  revolve  in  small  circles,  which  he  called  epicycles, 
which  were,  at  the  same  time,  carried  around  the  Earth  in 
larger  circles,  which  he  called  deferents,  or  carrying  circles. 

In  following  out  his  theory,  and  applying  it  to  the  explanation  of  different  phenomena, 
it  became  necessary  to  add  new  epicycles,  and  to  have  recourse  to  other  expedients,  until 
the  system  became  unwieldy,  cumbrous,  and  complicated.  This  theory,  although  astro- 
nomical observations  continued  to  be  made,  and  some  distinguished  astronomers  appeared 
fro ai  time  to  time,  was  the  prevailing  theory  until  the  middle  of  the  15th  century.  It  was 
not,  however,  always  received  with  implicit  confidence  ;  nor  were  its  difficulties  always 
entirely  unappreciated. 

Alphonso  X.,  king  of  Castile,  who  flourished  in  the  13th  century,  when  contemplating 
the  doctrine  of  the  epicycles,  exclaimed,  "  Were  the  universe  thus  constructed,  if  the 
Deity  had  called  me  to  his  councils  at  the  creation  of  the  world,  I  could  have  given  him 
good  advice."  He  did  not,  however,  mean  any  impiety  or  irreverence,  except  what  waa 
directed  against  the  system  of  Ptolemy. 

320.  About  the  middle  of  the  15th  century,  Copernicus,  a 
native  of  Thorn  in  Prussia,  conceiving  a  passionate  attachment 
to  the  study  of  astronomy,  quitted  the  profession  of  medicine, 
and  devoted  himself  with  the  most  intense  ardor  to  the  study  of 
this  science.     "  His  mind,"  it  is  said,  "  had  long  been  imbued 
with  the  idea  that  simplicity  and  harmony  should  characterize 
the  arrangements  of  the  planetary  system.     In  the  complication 
and  disorder  which  he  saw  reigned  in  the  hypothesis  of  Ptolemy, 
he  perceived  insuperable  objections  to  its  being  considered  as  a 
representation  of  nature." 

318.  His  system  of  astronomy?  What  singular  idea  and  reasoning?  819.  What 
difficulty  did  he  meet  with,  and  how  explain  it?  What  further  difficulty?  How  long 
did  this  theory  prevail?  What  anecdote  of  the  King  of  Castile?  820.  What  dis- 
tinguish"d  student  of  astronomy  now  arose?  His  impressions  in  regard  to  the  Ptoleraaki 
theory  T  His  own  rarlicr  cmiviVtinns?  What  other  Un.-orics  did  he  study? 


168  ASTRONOMY. 

In  the  opinions  of  the  Egyptian  sages,  in  those  of  Pythagcras,  Philolaus,  Aristarcbus,1 
and  Nicetas,  he  recognized  his  own  earliest  conviction  that  the  Earth  was  not  the  center 
of  the  universe.  His  attention  was  much  occupied  with  the  speculation  of  Martinua 
Oapella,  who  placed  the  Sun  between  Mars  and  the  Moon,  and  made  Mercury  and  Venus 
revolve  round  him  as  a  center,  and  with  the  system  of  Appollonius  Pergceus  who  made 
ill  the  planets  revolve  around  the  Sun,  while  the  Sun  and  Moon  were  carried  around  tho 
3arth  in  the  center  of  the  universe. 

321.  The  examination,  however,  of  various   hypotheses,  by 
Copernicus,  gradually  expelled  the  difficulties  with  which   the 
subject  was  beset,  and  after  the  labor  of  more  than  thirty  years, 
he  was  permitted  to  see  the  true  system  of  the  universe.     Tho 
Sun  he  considered  as  immovable,  in  the  center  of  the  system, 
while  the  Earth  revolved  around  him,  between  the  orbits  of 
Yenus  and  Mars,  and  produced  by  its  rotation  about  its  axis  all 
the  diurnal  phenomena  of  the  celestial  sphere.    The  other  planets 
he  considered  as  revolving  about  the  Sun,  in  orbits  exterior  to 
that  of  the  Earth.     ( See.  the  Relative  Distances  of  the  Planets' 
Orbits,  Map  I.  of  the  Atlas.) 

Thus,  the  stations  and  retrogradations  of  the  planets  were  the  necessary  consequence 
of  their  own  motions,  combined  with  that  of  the  Earth  about  the  Sun.  He  said  that  "  by 
long  observation,  he  discovered  that,  if  the  motions  of  the  planets  be  compared  with 
that  of  the  Earth,  and  be  estimated  according  to  the  times  in  which  they  perform  their 
revolutions,  not  only  their  several  appearances  would  follow  from  this  hypothesis,  but 
that  it  would  so  connect  the  older  of  the  planets,  their  orbits, magnitudes,  and  distances, 
and  even  the  apparent  motion  of  the  fixed  stars,  that  it  would  be  impossible  to  remove 
one  of  these  bodies  out  of  its  place  without  disordering  the  rest,  and  even  the  whole  of 
the  universe  also." 

322.  Soon  after  the  death  of  Copernicus,  arose  Tycho  Brahe, 
born  at  Knudstorp,  in  Norway,  in  1546.     Such  was  the  distinc- 
tion which  he  had  attained  as  an  astronomer,  that  when,  dissa- 
tisfied with  his  residence  in  Denmark,  he  had  resolved  to  remove, 
the  King  of  Denmark,  learning  his  intentions,  detained  him  in 
the  kingdom,  by  presenting  him  with  the  canonry  of  Rothschild, 
with  an  income  of  2,000  crowns  per  annum.     He  added  to  this 
sum  a  pension  of  1,000  crowns,  gave  him  the  island  of  Huen, 
and  established  for  him  an  observatory  at  an  expense  of  about 
200,000  crowns.     Here  Tycho  continued,  for  twenty-one  years, 
to  enrich  astronomy  with  his  observations. 

His  observations  upon  the  Moon  were  important,  and  upon  the  planets  numerous  and 
precise,  and  have  formed  the  data  of  the  present  generalizations  in  astronomy.  He, 
however,  rejected  the  system  of  Copernicus;  considering  the  Earth  as  immovable  in  the 
center  of  the  system,  while  the  Sun,  with  all  the  planets  and  comets  revolving  around 
him,  performed  his  revolution  around  the  earth,  and,  in  the  course  of  twenty-four  hours, 
the  stars  also  revolved  about  the  central  body.  This  theory  was  not  so  simple  as  that  of 
Copernicus,  and  involved  the  absurdity  of  making  the  Sun,  planets,  &c.,  revolve  around 
a  body  comparatively  insignificant. 

321.  How  was  Copernicus  led  to  discover  the  true  system  of  astronomy  ?    What  is  that 
system?     Does  it  account  for  the   stations  and  retrogradations  of  the  ilanets?        822 
What  distinguished  astronomer  next  arose?     What  said  of  his  detentioa  in  Denmark 
U is  observations?    His  theory 


PHENOMENA    0        ?.IE    SOLAR    SYSTEM. 

323.  Near  the  close  of  tht  15th  century,  arose  two  men,  who 
wrought  most  important  changes  in   the  science  ;   Kepler  and 
Galileo,  the  former  a  German,  the  latter  an  Italian.     Previous 
to  Kepler,  all  investigations  proceeded  upon  the  supposition  that 
the  planets  moved  in  circular  orbits  which  had  been  a  source  of 
much  error.     This  supposition  Kepler  showed  to  be  false.     He 
discovered  that  their  orbits  were  ellipses.     The  orbits  of  their 
secondaries  or  moons  he  also  found  to  be  the  same  curve.     He 
next  determined  the  dimensions  of  the  orbits  of  the  planets,  and 
found  to  what  their  velocities  in  thiir  motions  through  their 
orbits,  and  the  times  of  their  revolutions,  were  proportioned ;  all 
truths  of  the  greatest  importance  to  the  science. 

324.  While  Kepler  was  making  these  discoveries  of  facts,  very 
essential  for  the  explanation  of  many  phenomena,  Galileo  was 
discovering  wonders  in  the  heavens  never  before  seen  by  the  eye 
of  man.     Having  improved  the  telescope,  and  applied  it  to  the 
heavens,  he  observed  mountains  and  valleys  upon  the  surface  of 
our  Moon  ;  satellites  or  secondaries  were  discovered  revolving 
about  Jupiter ;  and  Venus,  as  Copernicus  had  predicted,  was 
seen  exhibiting  all  the  different  phases  of  the  Moon,  waxing  and 
waning  as  she  does,  through  variou§  forms. 

Many  minute  stars,  not  visible  to  the  naked  eye,  were  described  in  the  Milky- Way ;  and 
the  largest  fixed  stars,  instead  of  being  magnified,  appeared  to  be  small  brilliant  points, 
an  incontrovertible  argument  in  favor  of  their  immense  distance  from  us.  All  his  dis- 
coveries served  to  confirm  the  Oopernican  theory,  and  to  show  the  absurdity  of  the 
hypothesis  of  Ptolemy. 

325.  Although  the  general  arrangement  and  motions  of  the 
planetary  bodies,  together  with  the  figure  of  their  orbits,  had 
been  thus  determined,  the  force  of  power  which  carries  them 
around  in  their  orbits,  was  as  yet  unknown.     The  discovery  of 
this  was  reserved  for  the  illustrious  Newton,  though  even  his 
discovery   was   in   some   respects   anticipated    by   Copernicus, 
Kepler  and  Hooke*     By  reflecting  on  the  nature  of  gravity — 
that  power  which  causes  bodies  to  descend  toward  the  center  of 
the  earth — since  it  does  not  sensibly  diminish  at  the  greatest 
distance  from  the  center  of  the  earth  to  which  we  can  attain, 
being  as  powerful  on  the  loftiest  mountains  as  it  is  in  the  deepest 
caverns,  he  was  led  to  imagine  that  it  might  extend  to  the 
Moon,  and  that  it  might  be  the  power  which  kept  her  in  her 
orbit,  and  caused  her  to  revolve  around  the  Earth.     He  was 
next  led  t )  suppose  that  perhaps  the  same  power  carried  the 

828.  What  two  noted  astronomers  next  arose  ?  What  did  Kepler  discover  ?  824. 
Galileo  and  his  discoveries?  What  theory  did  they  serve  to  establish?  825  Wha', 
pe-at  discovery  next  made,  and  by  whom!  How  le-1  to  it?  Successive  atepo? 


170  ASTRONOMY. 

primary  plants  around  the  Sun.  By  a  series  of  calculations, 
he  was  enabled  at  length  to  establish  the  fact,  that  the  same 
force  which  determines  the  fall  of  an  apple  to  the  Earth,  carries 
the  moons  in  their  orbits  around  the  planets,  and  the  planets 
and  comets  in  their  orbits  around  the  Sun. 

To  recapitulate  briefly  :  The  system  (not  hypothesis,  for  much  of  it  has  been  established 
by  mathematical  demonstration)  by  which  we  are  now  enabled  to  explain  with  a  beauti- 
fu'  simplicity  the  different  phenomena  of  the  Sun,  planets,  moons,  and  comets,  is,  that 
tbo  Sun  is  the  central  body  in  the  system:  that  the  planets  and  comets  move  round  him 
in  elliptical  orbits,  whose  planes  are  more  or  less  inclined  to  each  other,  with  velocities 
bearing  to  each  other  a  certain  ascertained  relation,  and  in  times  related  to  their  dis- 
tances ;  that  the  moons,  or  secondaries,  Devolve  in  like  manner  about  their  primaries, 
and  at  the  same  time  accompany  them  in  their  motion  around  the  Sun ;  all  meanwhile 
revolving  on  axes  of  their  own  ;  and  that  these  revolutions  in  their  orbits  are  produced 
by  the  mysterious  power  of  attraction.  The  particular  mode  in  which  this  system  is 
applied  to  the  explanation  of  the  different  phenomena,  will  be  exhibited  as  we  proceed  to 
consider,  one  by  one,  the  several  bodies  above  mentioned. 

326.  These  bodies,  thus  arranged  and  thus  revolving,  consti- 
tute what  is  termed  the  Solar  System.  The  planets  have  been 
divided  into  two  classes,  primaries  and  secondaries.  The  latter 
are  also  termed  moons,  and  sometimes  satellites.  The  primaries 
are  those  that  revolve  about  the  Sun,  as  a  center.  The  seconda- 
ries are  those  which  revolve  about  the  primaries.  There  have 
been  discovered  to  this  date  (1854),  thirty-five  primary  planets, 
viz. :  Mercury,  Venus,  the  Earth,  Mars,  Flora,  Clio,  Vesta,  Iris, 
Metis,  Eunomia,  Psyche,  Thetis,  Melpomene,  Fortuna,  Massilia, 
Lutetia,  Calliope,  Thalia,  Hebe,  Parthenope,  Irene,  Egeria, 
AstraBa,  Juno,  Ceres,  Pallas,  Hygeia,  Jupiter,  Saturn,  Uranus, 
Neptune,  and  four  other  Asteroids,  whose  names  and  places  have 
not  yet  been  determined.  Mercury  is  the  nearest  to  the  Sun, 
and  the  others  follow  in  the  order  in  which  they  are  named.  The 
seventeen  small  planets  from  Flora  to  Hygeia,  inclusive,  were  dis- 
covered by  means  of  the  telescope,  and,  because  they  are  very 
small,  compared  with  the  others,  are  called  Asteroids.  Neptune, 
also,  is  a  telescopic  planet,  though  much  larger  than  any  of  the 
Asteroids. 

There  have  been  discovered  twenty  secondaries.  Of  these, 
the  Earth  has  one,  Jupiter  four,  Saturn  eight,  Hersckel  six,  and 
Neptune  one.  All  these,  except  our  Moon,  as  well  as  the  Aste- 
roids and  Neptune,  are  invisible  to  the  naked  eye. 

Map  I.  of  the  Atlas,  "  exhibits  a  plan  of  the  Solar  System,"  comprising  the  relative 
magnitudes  of  the  Sun  and  Planets  ;  their  comparative  distances  from  the  Sun,  and  from 
each  other;  the  position  of  their  orbits,  with  respect  to  each  other;  the  Earth  and  the 
Sun  ;  together  with  many  other  particulars  which  are  explained  on  the  map.  There,  the 

Describe  the  Copernican  theory?  326.  What  do  the  bodies  mentioned  ceistitutc? 
How  are  the  planets  divided?  Describe  each?  What  number  of  primaries  ?  Name 
them  in  order  from  the  Sun  ?  Which  are  the  Asteroids  ?  Which  telescopic  ?  How  many 
£,ecoml;viy  planets?  How  dtetriljiuvd?  Arc  they  visible  to  the  nuked  tifcf  What  rfuij 


THE    SUN HIS    DISTANCE,    MAGNITUDE,    ETC.  171 

flrft  and  most  prominent  object  which  claims  attention,  is  the  representation  of  the 
Sun's  circumference,  with  its  deep  radiations,  bounding  the  upper  margin  of  the  map. 
It  is  apparent,  however,  that  this  segment  is  hardly  one-sixth  of  the  whole  circumference 
of  which  it  is  a  part.  Were  the  map  sufficiently  large  to  admit  the  entire  orb  of  the  Sun, 
even  upon  so  diminutive  a  scale  as  there  represented,  we  should  then  see  the  Sun  and 
Planets  in  their  just  proportions — the  diameter  of  the  former  being  112  times  the  diameter 
of  the  Earth. 

It  was  intended,  originally,  to  represent  the  Earth  upon  a  scale  of  one  inch  in  diameter 
and  the  other  bodies  in  that  proportion ;  but  it  was  found  that  it  would  increase  the  map 
to  four  times  its  size  ;  and  hence  it  became  necessary  to  assume  a  scale  of  half  an  inch 
for  the  Earth's  diameter,  which  makes  that  of  the  Sun  56  inches,  and  the  other  bodies,  as 
represented  upon  the  map. 

The  relative  position  of  the  Planets'  orbits  is  also  represented,  on  a  scale  as  large  as 
the  sheet  would  permit.  Their  relative  distances  from  the  Sun  as  a  center,  and  from  each 
other,  are  there  shown  correctly.  But  had  we  wished  to  enlarge  the  dimensions  of  these 
orbits,  so  that  they  would  exactly  correspond  with  the  scale  to  which  we  have  drawn  tho 
planets,  the  map  must  have  been  nearly  two  miles  in  length.  *'  Hence,"  says  Sir  John 
Herschel,  "  the  idea  that  we  can  convey  correct  notions  on  this  subject,  by  drawing  circles 
on  paper,  is  out  of  the  question." 

To  illustrate  this — Let  us  suppose  ourselves  standing  on  an  extended  plane,  or  field  of 
ice,  and  that  a  globe  4  feet  8  inches  in  diameter  is  placed  in  the  center  of  the  plane,  to 
represent  the  Sun.  Having  cut  out  of  the  map  the  dark  circles  representing  the  planets, 
we  may  proceed  to  arrange  them  in  their  respective  orbits  about  the  Sun,  as  follows  : 

First,  we  should  take  Mercury,  about  the  size  of  a  smill  currant,  and  place  it  on  the 
circumference  of  a  circle  194  feet  from  the  Sun;  this  circle  would  represent  the  orbit  of 
Mercury,  in  the  proper  ratio  of  its  magnitude.  Next,  we  should  take  Venus,  about  the 
size  of  a  rather  small  cherry,  and  place  it  on  a  circle  862  feet  from  the  Sun,  to  represent 
the  orbit  of  Venus.  Then  would  come  the  Earth,  about  the  size  of  a  cherry,  revolving  in 
an  orbit  500  feet  from  the  Sun.  After  the  Earth  we  should  place  Mars,  about  the  size  of 
a  cranberry,  on  a  circle  T62  feet  from  the  Sun.  Neglecting  the  Asteroids,  some  of  which 
would  not  be  larger  than  a  pin's  head,  we  should  place  Jupiter,  hardly  equal  to  a  mode- 
rate-sized melon,  on  a  circle  at  the  distance  of  half  a  mile  (2601  feet)  from  the  Sun ; 
Saturn,  somewhat  less,  on  a  circle  nearly  a  mile  (4768  feet)  from  the  Sun  ;  Herschel,  about 
the  size  of  a  peach,  on  the  circumference  of  a  circle  nearly  2  miles  (9591  feet)  from  the 
Sun  ;  and  last  of  all  Neptune,  a  little  larger  than  Herschel,  and  on  a  circle  of  nearly  3 
miles  (15,366  feet)  from  the  Sun. 

To  imitate  the  motions  of  the  planets  in  the  above-mentioned  orbits,  Mercury  must 
describe  its  own  diameter  in  41  seconds ;  Venus,  in  4  minutes  14  seconds  ;  the  Earth,  in 
T  minutes;  Mars,  in  4  minutes  48  seconds;  Jupiter,  in  2  hours  56  minutes;  Saturn,  in 
8  hours  13  minutes;  Herschel,  in  12  hours  16  minutes  ;  and  Neptune,  in  23  honrs  25  min. 

Many  other  interesting  subjects  are  embraced  in  Map  I. ;  but  they  are  either  explained 
on  the  map,  or  in  the  following  chapters,  to  which  they  respectively  relate. 


CHAPTER  II. 

THE    SUN— HIS    DISTANCE,    MAGNITUDE,    &c. 

321.  THE  Sun  is  a  vast  globe,  in  the  center  of  the  solar  sys- 
tem, dispensing  light  and  heat  to  all  the  planets,  and  governing 
all  their  motions.  It  is  the  great  parent  of  vegetable  life,  giv- 
ing warmth  to  the  seasons,  and  color  to  the  landscape.  Its  rays 
are  the  cause  of  various  phenomena  on  the  surface  of  the  earth 
and  in  the  atmosphere.  By  their  agency,  all  winds  are  pro- 
of Map  I.?  Its  soile?  Remark  of  Dr.  Hcrtichel?  What  illustrations  of  the  8<>'ar  Syatoin 
does  he  furnish?  827.  Sucjeu  cf  Chapter  II.?  Describe-  the  Sun? 

B.G.  b 


172 


ASTRONOMY. 


duced,  aiid  the  waters  of  the  sea  are  made  to  circulate  in  vapor 
through  the  air,  aud  irrigate  the  land,  producing  springs  and  rivers. 
328.  The  Sun  is  by  far  the  largest  of  the  heavenly  bodies 
whose  dimensions  have  been  definitely  ascertained.  Its  diameter 
is  about  889,000  miles.  Consequently,  it  contains  a  volume 
of  matter  equal  to  fourteen  hundred  thousand  globes  of  the  size 
of  the  Earth.  Of  a  body  so  vast  in  its  dimensions,  the  human 
mind,  with  all  its  efforts,  can  form  no  adequate  conception. 

THE  SUN  AND  THE  MOON'S  ORBIT.  Were  the  Sun  a  hollow  sphere,  perforated  with 

a  thousand  openings  to  admit  the  twinkling  of 
the  luminous  atmosphere  around  it — and  were  a 
globe  as  large  as  the  Earth  placed  at  its  center, 
with  a  satellite  as  large  as  our  Moon,  and  at  the 
same  distance  from  it  as  she  is  from  the  earth, 
there  would  be  present  to  the  eye  of  a  spectator 
on  the  interior  globe,  a  universe  as  splendid  as 
that  which  now  appears  to  the  uninstructed  eye 
— a  universe  as  large  and  extensive  as  the 
whole  creation  was  conceived  to  be  in  the 
infancy  of  astronomy. 

The  mean  distance  of  the  Moon  from  the 
Earth  is  240,000  miles,  consequently  the  average 
diameter  of  her  orbit  is  480,000  miles  ;  and  yet, 
were  the  Sun  to  take  the  place  of  the  Earth,  he 
would  fill  the  whole  orbit  of  the  Moon,  and 
extend  200,000  miles  beyond  it  in  every  direc- 
tion !  To  pass  from  side  to  side  through  his 
center,  at  railroad  speed  (30  miles  an  hour), 
would  require  nearly  three  and  a  half  years , 
and  to  traverse  his  vast  circumference  nearly  eleven  years. 

Here  let  the  student  refer  to  Map  I.,  where  the  Relative  Magnitudes  of  the  Sun  and 
Planets  are  exhibited.  Let  him  compare  the  segment  of  the  Sun's  circumference,  aa 
there  represented,  with  the  entire  circumference  of  the  Earth.  They  are  both  drawn  upou 
the  same  scale.  The  segment  of  the  Sun's  circumference,  since  it  is  almost  a  straight 
line,  must  be  a  very  small  part  of  what  the  whole  circumference  would  be,  were  it  repre- 
sented entire.  Let  the  student  understand  this  diagram,  and  he  will  be  in  some  measure 
able  to  conceive  how  like  a  mere  point  the  Earth  is,  compared  with  the  Sun,  and  to  form 
in  his  mind  some  image  of  the  vast  magnitude  of  the  latter. 

V"  329.  The  next  thing  which  fills  the  mind  with  wonder,  is  the 
distance  at  which  so  great  a  body  must  be  placed,  to  occupy, 
apparently,  so  small  a  space  in  the  firmament.  The  Sun's  mean 
distance  from  the  Earth  is  twelve  thousand  times  the  Earth's 
diameter,  or  a  little  more  than  95,000,000  of  miles.  We  may 
derive  some  faint  conception  of  such  a  distance,  by  considering 
that  the  swiftest  steamboats,  which  ply  our  waters  at  the  rate 
of  200  miles  a  day,  would  not  traverse  it  in  thirteen  hundred 
years;  and,  that  a  cannon  ball,  flying  night  and  day,  at  the 
rate  of  16  miles  a  minute,  would  not  reach  it  in  eleven  years. 

330.  The  Sun,  when  viewed  through  a  telescope,  presents  the 
appearance  of  an  enormous  globe  of  fire,  frequently  in  a  state  of 
violent  agitation  or  ebullition  ;  dark  spots  of  irregular  form, 

S'Jb.  His  magnitude?  Diameter?  Compared  with  the  Earth  ?  What  illustration  given? 
What  reference  to  the  Map?  329.  Distance  of  the  Sun?  What  illustration  given « 
4HH  How  does  the  Sun  appear  through  a  ttJcjcopo?  Describe  those  rpotj? 


THE    SUN HIS    DISTANCE.    MAGNITUDE,    ETC.  173 

rarely  visible  to  the  naked  eye,  frequently  pass  over  his  disc, 
from  east  to  west,  in  the  period  of  nearly  fourteen  days. 

Th*»«e  spots  are  usually  surrounded  by  a  SPOTS  on  THE  SCN. 

penumbra,  or  less  deeply  shaded  border, 
and  that,  by  a  margin  of  light  more  bril- 
liant that  that  of  the  Sun.  A  spot  when 
first  seen  on  the  eastern  edge  of  the  Sun, 
appears  like  a  line  which  progressively  ex- 
tends in  breadth,  and  increases  its  appa- 
rent velocity,  till  it  reaches  the  middle, 
when  it  begins  to  contract,  and  to  move 
less  rapidiy,  till  it  ultimately  disappears  at 
the  western  edge.  In  some  rare  instances, 
the  same  spots  re-appear  on  the  east  side, 
and  are  permanent  for  two  or  three  revo- 
lutions. But,  as  a  general  thing,  the  spots 
on  the  fun  are  neither  permanent  nor  uni- 
form. Sometimes  several  small  ones  unite 
into  a  large  one;  and,  again,  a  large  one 
separates  into  numerous  small  ones.  Some 
continue  several  days,  weeks,  and  even 
months,  together;  while  others  appear  and 
disappear,  in  the  course  of  a  few  hours. 
Those  spots  that  are  formed  gradually,  are, 
for  the  most  part,  as  gradually  dissolved  ; 
whilst  those  that  are  suddenly  formed,  generally  vanish  as  quickly. 

331.  It  is  the  general  opinion,  that  spots  on  the  Sun  were 
first  discovered  by  Galileo,  in  the  beginning'  of  the  year  1611  ; 
though  Scheiner,  Harriot,  and  Fabricius,  observed  them  about 
the  same  time.  During  a  period  of  18  years  from  this  time,  the 
Sun  was  never  found  entirely  clear  of  spots,  excepting  a  few 
days  in  December,  1624  :  at  other  times,  there  were  frequently 
seen  twenty  or  thirty  at  a  time,  and  in  1625,  upwards  of  fifty 
were  seen  at  once.  From  1650  to  1670,  scarcely  any  spots  were 
to  be  seen  ;  and,  from  1676  to  1684,  the  orb  of  the  Sun  pre- 
sented an  unspotted  disc.  Since  the  beginning  of  the  eighteenth 
century,  scarcely  a  year  has  passed,  in  which  spots  have  not 
been  visible,  and  frequently  in  great  numbers.  In  1799,  Dr 
Herschel  observed  one  nearly  30,000  miles  in  breadth. 

A  single  second  of  angular  measure,  on  the  Sun's  disc,  as  seen  from  the  Earth,  corre- 
sponds to  462  miles ;  and  a  circle  of  this  diameter  (containing  therefore  nearly  220,000 
square  miles)  is  the  least  space  which  can  be  distinctly  discerned  on  the  Sun  as  a  vitiblt) 
area,  even  by  the  most  powerful  glasses.  Spots  have  been  observed,  however,  whose 
linear  diameter  has  been  more  than  44,000  miles;  and,  if  some  records  are  to  be  trusted, 
of  even  still  greater  extent. 

DR.  DICK,  in  a  letter  to  the  author,  says :  "  I  have  for  many  years  examined  the  solar 
spots  with  considerable  minuteness,  and  have  several  times  seen  spots  which  were  not 
less  than  the  one  twenty-fifth  part  of  the  Sun's  diameter,  which  would  make  them  about 
?2,192  miles  in  diameter,  yet  they  were  visible  neither  to  the  naked  eye,  nor  through  an 
opera  glass  magnifying  about  three  times.  And,  therefore,  if  any  spots  have  been  vist 
ble  to  the  naked  eye — which  we  must  believe,  unless  we  refuse  respectable  testimony— 
they  could  not  have  been  much  less  than  50,000  miles  in  diameter." 

83i  Who  first  saw  them?  When?  How  was  it  for  the  next  IS  years?  How  in  1625 '•' 
From  1650tol(5<0?  From  1676  to  1684?  How  since  the  beginning  of  the  eighteenth 
sectary?  Dr.  Herschel's  measurements?  Dr.  Dick's  remarks  and  conclusion ? 


174 


ASTRONOMY. 


332.  The  apparent  direction  of  these  spots  over  the  Sun's  disc 
is  continually  varying.     Sometimes  they  seem  to  move  across  it 
in  straight  lines,  at  others  in  curve  lines.     Sometimes  the  spots 
seem  to  move  upward,  as  they  cross  from  east  to  west,  while  at 
other  times  they  incline  downward,  while  the  curve  lines  are 
sometimes  convex  towards  one  pole  of  the  Sun,  and  sometimes 
towards  the  other. 

333.  All  these  phenomena  are  owing  to  the  fact  that  the  axis 
of  the  Sun  is  inclined  to  the  ecliptic,  so  that  viewing  him  from 
different  points  in  the  Earth's  orbit,  the  apparent  direction  of 
the  spots  must  necessarily  vary.     The  following  diagrams  may 
serve  to  illustrate  : 


VARIOUS  DIRECTIONS  OF  THE  SOLAR  SPOTS. 

B  C 

I 


March. 


Jmve. 


September.  December. 

Let  E  P  represent  the  plane  of  the  ecliptic.  In  March,  the  spots  describe  a  curve, 
which  is  convex  to  the  south,  as  shown  at  A.  In  June,  they  cross  the  Sun's  disc  in  nearly 
straight  lines,  but  incline  upward.  In  September,  they  curve  again,  though  in  the  oppo- 
site direction  ;  and  in  December,  pass  over  in  straight  lines,  inclining  downward.  The 
figures  B  and  D  show  the  inclination  of  the  Sun's  axis. 

The  following  diagram  will  servo  still  further  to  illustrate  the 
cause  of  the  change  of  direction  of  the  solar  spots. 

SOLAR  SPOTS  OBSERVED   FROM   DIFFERENT    POINTS. 


Let  the  student  imagine  himself  stationed  upon  the  earth  at  A,  in  March,  looking  upon 
the  stm  in  the  center,  whose  north  or  upper  pole  is  now  inclined  toward  him.  The  spots 
will  then  curve  Uvjiward.  TJiree  months  afterward — vis.,  in  June — the  earth  will  be 


832.  In  what  general  direction  do  these  spots  move  ?    What  variations  T 
Is  the  oazwt'  of  these  varying  phenomena? 


838.  Whaf, 


THE    SUN HIS    DISTANCE,    MAGNITUDE,    ETC.  175 

at  B ;  when  the  sun's  axis  will  incline  to  tlie  left,  and  the  spots  seem  to  pass  upward  to 
the  right.  In  three  months  longer,  the  observer  will  be  at  C,  when  the  north  pole  of  the 
sun  will  incline/row  iiim,  and  the  spots  seem  to  curve  upward ;  and  in  three  months 
longer,  he  will  be  at  D,  when  the  axis  of  the  sun  will  incline  to  the  right,  and  the  spots 
seem  to  incline  downward. 

334.  From  the  regularity  with  which  these  spots  revolve,  it 
is  concluded,  with  good  reason,  that  they  adhere  to  the  surface 
of  the  Sun  and  revolve  with  it.     They  are  all  found  within  30° 
of  his  equator,  or  within  a  zone  60  in  width. 

335.  The  apparent  revolution  of  a  spot,  from  any  particular 
point  of  the  Sun's  disc,  to  the  same  point  again,  is  accomplished 
in  27  days,  7  hours,  26  minutes,  and  24  seconds  ;  but  during 

oat  time,  the  spot  has,  in  fact,  gone  through  one  revolution, 
together  with  an  arc,  equal  to  that  described  by  the  Earth  in 
ner  orbit  in  the  same  time  ;  which  reducest  he  time  of  the  Sun's 
actual  rotation  on  his  axis,  to  25  days,  9  hours,  and  36  minutes. 

Let  S  represent  the  sun,  and  A       SIDEREAL  AND  SYNODIC  REVOLUTION'S  OF  THE  SUN. 
the  earth  in  her  orbit.    When  she 
is  at  A,  a  spot  is  seen  upon  the  / 

disc  of  the  sun  at  B.  The  sun  re- 
volves in  the  direction  of  the  ar- 
rows, and  in  25  days  10  hours  the 
spot  comes  round  to  B  again,  or 
opposite  the  star  E.  This  is  a  side- 
real revolution. 

During  these  25  days  8  hours, 
the  earth  has  passed  on  in  her 
orbit  some  25",  or  nearly,  to  C, 
which  will  require  nearly  two  days 
for  the  spot  at  B  to  get  directly 
toward  the  earth,  as  shown  at  D.  ^a&v 
This  last  is  a  synodic  revolution. 
It  consists  of  one  complete  revolu-  *• 

tion  of  the  sun  upon  his  axis,  and 
about  27°  over 

336.  The  part  of  the  Sun's  disc  not  occupied  by  spots,  is  far 
from  being  uniformly  bright.     Its  ground  is  finely  mottled  with 
an  appearance  of  minute  dark  dots,  or  pores,  which,  attentively 
watched  for  several  days  in  succession,  are  found  to  be  in  a  con- 
stant state  of  change. 

What  the  physical  organization  of  the  Sun  may  be,  is  a  ques- 
tion which  astronomy,  in  its  present  state,  cannot  solve.  It 
seems,  however,  to  be  surrounded  by  an  ocean  of  inexhaustible 
flame,  with  dark  spots  of  enormous  size,  now  and  then  floating 
upon  its  surface.  From  these  phenomena,  Sir  W.  Herschel  sup- 
posed the  Sun  to  be  a  solid,  dark  body,  surrounded  by  a  vast 

834.  Are  these  spots  supposed  to  adhere  to  the  body  of  the  Sun  ?  On  what  part  of  the 
Sun  arc  they  found  ?  835.  What  is  their  time  of  apparent  revolution  ?  The  actual 
time?  How  arrived  at?  336.  What  said  of  the  part  of  the  Su-i  about  his  poles?  Of 
his  physical  organization?  What  Joes  it  seem  to  be9  How  did  Sir  W.  Hersrhol 
regard  it? 


176  ASTRONOMY. 

atmosphere,  almost  always  filled  with  luminous  clouds,  occasion- 
ally opening  and  disclosing  the  dark  mass  within. 

337.  The  speculations  of  Laplace  were   different.     He  im- 
agined the  solar  orb  to  be  a  mass  of  fire,  and  the  violent  effer- 
vescences and  explosions  seen  on  its  surface,  to  be  occasioned  by 
the  eruption  of  elastic  fluids,  formed  in  its  interior,  and  the  spots 
to  be   enormous   caverns,   like   the   craters   of  our  volcanoes. 
Others  have  conjectured  that  these  spots  are  the  tops  of  solar 
mountains,  which  are  sometimes  left  uncovered  by  the  luminous 
fluid  in  which  they  are  immersed. 

338.  Among   all    the    conflicting   theories   that   have   been 
advanced,  respecting  the  physical  constitution  of  the  Sun,  there 
is  none  entirely  free  from  objection.     The  prevailing  one  seems 
to  be,  that  the  lucid  matter  of  the  Sun  is  neither  a  liquid  sub- 
stance, nor  an  elastic  fluid,  but  that  it  consists  of  luminous 
clouds,  floating  in  the  Sun's  atmosphere,  which  extends  to  a 
great  distance,  and  that  these  dark  spots  are  the  opaque  body 
of  the  Sun,  seen  through  the  openings  in  his  atmosphere.     Iler- 
schel  supposes  that  the  density  of  the  luminous  clouds  need  not 
be  greater  than  that  of  our  Aurora  Borealis,  to  produce  the 
effects  with  which  we  are  acquainted. 

339.  The  similarity  of  the  Sun  to  the  other  globes  of  Jie  sys- 
tem, in  its  s  ipposed  solidity,  atmosphere,  surface  diverc  jedwith 
mountains  and  valleys,  and  rotation  upon  its  axis,  has  ied  to  the 
conjecture  that  it  is  inhabited,  like  the  planets,  by  beings  whose 
organs  are  adapted  to  their  peculiar  circumstances.     Such  was 
the  opinion  of  the  late  Dr.  Herschel,  who  .observed  it  unremit- 
tingly, with  the  most  powerful  telescopes,  for  a  period  of  fifteen 
years.     Such,  too,  was  the  opinion  of  Dr.  Elliot,  who  attributes 
to  it  the  most  delightful  scenery  ;  and,  as  the  light  of  the  Sun 
is  eternal,  so,  he  imagined,  were  its  seasons.     Hence  he  infers 
that  this  luminary  offers  one  of  the  most  blissful  habitations  for 
intelligent  beings  of  which  we  can  conceive. 

887.  Laplace's  speculations?  What  other  opinions?  838.  Is  there  a  satisfactory 
theory  of  the  physical  nature  of  the  Sun?  State  the  prevailing  i  ne  ?  Herschel's  suppo- 
sition? 839.  What  conjecture  in  regard  to  the  inhabitants  of  the  Sun,  and  is;1:,  a 
*hat  f<  unded  ?  Who  held  to  this  idea  ? 


y 


TOE    PRIMARY    PLANETS — MERCURY    AND    VENUS.       177 

CHAPTER  III. 

THE  PRIMARY  PLANETS-MERCURY  AND  VENUS. 


340.  MERCURY  is  the  nearest  planet  to  the  Sun  that  has  yet 
been  discovered ,  and  with  the  exception  of  the  asteroids,  is  the 
smallest.  Its  diameter  is  about  3,000  miles.  Its  bulk,  therefore, 
is  about  sixteen  times  less  than  that  of  the  Earth.  It  would 
require  more  than  twenty  millions  of  such  globes  to  compose  a 
body  equal  to  the  Sun. 

Here  the  student  should  refer  to  the  diagrams,  exhibiting  the  relative  magnitudes  and 
distances  of  the  Sun  and  Planets,  Map  I.  And  whenever  this  subject  recurs  in  the  course 
of  this  work,  the  student  should  recur  to  the  figures  of  this  Map,  until  he  is  able  to  form 
in  his  mind  distinct  conceptions  of  tne  relative  magnitudes  and  distances  of  all  the 
planets.  The  Sun  and  planets  being  spheres,  or  nearly  so,  their  relative  bulks  are  esti- 
mated by  comparing  the  cubes  of  their  diameters :  thus,  the  diameter  of  Mercury  being 
8,140  miles,  and  that  of  the  Earth  7,912 ;  their  bulks  are  as  the  cube  of  8,140,  to  the  cube 
of  7,912,  or  as  1  to  16,  nearly. 

K341.  Mercury  revolves  on  its  axis  from  west  to  east  in  24 
hours,  5  minutes,  and  28  seconds  ;  which  makes  its  day  about 
10  minutes  longer  than  ours.  It  performs  its  revolution  about 
the  Sun  in  a  few  minutes  less  than  88  days,  and  at  a  mean  dis- 
tance of  nearly  37,000,000  of  miles.  The  length  of  Mercury's 
year,  therefore,  is  equal  to  about  three  of  our  months. 

The  rotation  of  a  planet  on  its  axis,  constitutes  its  day ;  its  revolution  about  the  Sun 
Constitutes  its  year. 

342.  Owing  to  the  dazzling  brightness  of  Mercury,  the  swift- 
ness of  its  motion,  and  its  nearness  to  the  Sun,  astronomers 
have  made   but  comparatively   few   discoveries   respecting  it. 
When  viewed  through  a  telescope  of  considerable  magnifying 
power,  it  exhibits  at  different  periods  all  the  various  phases  of 
the  Moon  ;  except  that  it  never  appears  quite  full,  because  its 
enlightened   hemisphere  is   never   turned  directly  towards   the 
Earth,  only  when  it  is  behind  the  Sun,  or  so  near  to  it  as  to  be 
hidden  by  the  splendor  of  its  beams.     Its  enlightened  hemisphere 
being  thus  always  turned  towards  the  Sun,  and  the  opposite  one 
being  always  dark,  prove  that  it  is  an  opaque  body,  similar  to 
the  Earth,  shining  only  in  the  light  which  it  receives  from  the 
Sun. 

343.  Mercury  is  not  only  the  most  dense  of  all  the  planets, 
but  receives  from  the  Sun  six  and  a  half  times  as  much  light  and 

840.  Subject  of  Chapter  III.  ?  Size  and  position  of  Mercury  ?  What  map  illustrates 
this  subject?  841.  State  the  time  of  Mercury's  revolution  upon  his  axis?  How  doe:i 
tlr'i  compare  with  the  Earth?  His  period  of  revolution  around  the  Sun  ?  842.  What 
eaid  of  discoveries  upon  Mercury,  his  phases,  &c.  ?  What  proof  that  he  is  opaque  ? 


178 


ASTRONOMY. 


heat  as  the  Earth.  The  truth  of  this  estimate,  of  course, 
depends  upon  the  supposition  that  the  intensity  of  solar  light  and 
heat  at  the  planets,  varies  inversely  as  the  squares  of  their  dis- 
tances from  the  Sun. 


PHILOSOPHY  OF  THB  DIFFUSION  OP  LIGHT. 


In  this  diagram  the  light  is  seen  passing  in  right  lines,  from  the  sun  on  the  left  toward 
the  several  planets  on  the  right.  It  is  also  shown  that  the  surfaces  A,  B,  and  C  receive 
equal  quantities  of  light,  though  B  is  four  times,  and  C  nine  times  as  large  as  A ;  and  as 
the  light  falling  upon  A  is  spread  over  four  times  as  much  surface  at  B,  and  nine  times  as 
much  at  C,  it  follows  that  it  is  only  one-ninth  as  intense  at  C,  and  one-fourth  at  B,  as  it 
is  at  A.  Hence  the  rule,  that  the  light  and  heat  of  the  planet  is,  inversely,  as  the  squa  re* 
of  their  respective  distances. 

The  student  may  not  exactly  understand  this  last  statement.  The  square  of  any  num. 
ber  is  its  product,  when  multiplied  by  itself.  Now  suppose  we  call  the  distances  A,  B, 
and  C,  1,  2,  and  3  miles.  Then  the  square  of  1  is  1 ;  the  square  of  2  is  4;  and  the  square 
of  3  is  9.  The  light  and  heat,  then,  would  be  in  inverse  proportion  at  these  three  points, 
as  1,  4,  and  9 ;  that  is,  four  times  less  at  B  than  at  A,  and  nine  times  less  at  0.  These 
amounts  we  should  state  as  1,  M.  and  one-ninth. 

344.  This  law  of  analogy,  did  it  exist  with  rigorous  identity 
at  all  the  planets,  would  be  no  argument  against  their  being 
inhabited  ;  because  we  are  bound  to  presume  that  the  All-wise 
Creator  has  attempered  every  dwelling-place  in  his  empire  to  the 
physical  constitution  of  the  beings  which  he  has  placed  in  it. 

From  a  variety  of  facts  which  have  been  observed  in  relation  to  the  production  of 
r.aloric,  it  does  not  appear  probable,  that  the  degree  of  heat  on  the  surface  of  the  differ- 
ent planets  depends  on  their  respective  distances  from  the  Sun.  It  is  more  probable,  that 
it  depends  chiefly  on  the  distribution  of  the  substance  of  caloric  on  the  surfaces,  and 
throughout  the  atmospheres  of  these  bodies,  in  different  quantities,  according  to  the  dif- 
ferent situations  which  they  occupy  in  the  solar  system  ;  and  that  these  different  quanr 
tities  of  caloric  are  put  into  action  by  the  influence  of  the  solar  rays,  so  as  to  produce 
that  degree  of  sensible  heat  requisite  to  the  wants,  and  to  the  greatest  benefit  of  each  of 
the  planets.  On  this  hypothesis,  which  is  corroborated  by  a  great  variety  of  facts  and 
experiments,  there  may  be  no  more  sensible  heat  experienced  on  the  planet  Mercury, 
than  on  the  surface  of  Herschel,  which  is  fifty  times  farther  removed  from  the  Sun. 

345.  The  rotation  of  Mercury  on  its  axis,  was  determined 
from  the  daily  position  of  its  horns,  by  M.  Schroeter,  who  not 
only  discovered  spots  upon  its  surface,  but  several  mountains  in 
its  southern  hemisphere,  one  of  which  was  lOf  miles  high— 
nearly  three  times  as  high  as  Chimborazo,  in  South  America. 

843.  His  density,  and  light  and  heat?  Upon  what  rule  is  this  estimate  based?  844. 
Would  not  this  law  of  analogy  make  against  the  doctrine  that  the  planets  are  inhab- 
ited ?  Is  it  probable  that  this  law  does  prevail?  Upon  what  may  the  relative  heat  of  the 
pJanets  depend?  345.  How  was  his  diurnal  revolution  determined,  and  by  whomV 
What  said  of  his  surface  ?  What  observation  respecting  mountains  in  general  ? 


ME    PRIMARY    PLANETS MERCURY    AND    VENUS.        179 

U  is  worthy  of  observation,  that  the  highest  mountains  which  have  been  discovered  ii, 
Mercury,  Venus,  the  Moon,  and  perhaps  we  may  add  the  Earth,  are  all  situated  in  theii 
southern  hemispheres. 

346.  During  a  few  days  in  March  and  April,  August  and  Sep- 
tember, Mercury  may  be  seen  for  several  minutes,  in  the  morn- 
ing or  evening  twilight,  when  its  greatest  elongations  happen  io 
those  months  ;  in  all  other  parts  of  its  orbit,  it  is  too  near  the 
Sun  to  be  seen  by  the  naked  eye.     The  greatest  distance  that  it 
ever  departs  from  the  Sun,  on  either  side,  varies  from  16°  12', 
to  28°  20',  alternately. 

The  distance  of  a  planet  from  the  Sun,  as  seen  from  the  Earth 
(measured  in  degrees),  is  called  its  elongation.  The  greatest 
absolute  distance  of  a  planet  from  the  Sun  is  denominated  its 
aphelion,  and  the  least  its  perihelion. 

347.  The  revolution  of  Mercury  about  the  Sun,  like  that  of 
all  the  planets,*  is  performed  from  west  to  east,  in  an  orbit  which 
is  nearly  circular.     Its  apparent  motion,  as  seen  from  the  Earth, 
is,  alternately,  from  west  to  east,  and  from  east  to  west,  nearly 
in  straight  lines  ;  sometimes  directly  across  the  disc  of  the  Sun, 
but  at  all  other  times  either  a  little  above  or  a  little  below  it. 

Were  the  orbits  of  Mercury  and  Venus  in  the  same  plane  with  that  of  the  Earth,  they 
would  cross  the  Sun's  disc  at  every  revolution  ;  but  as  one-half  of  each  of  their  orbits  ia 
fbo<ve,  and  the  other  half  below  the  ecliptic,  they  generally  appear  to  pass  either  above 
or  below  the  Sun. 


Let  the  right  line  A,  joining  the  Earth  and  the  Sun  in  the  above  diagram,  represent 
the  plane  of  the  ecliptic.  Now  when  an  interior  planet  is  in  this  plane,  as  shown  at  A, 
it  may  appear  to  be  upon  the  Sun's  disc  ;  but  if  it  is  either  above  or  below  the  ecliptic, 
as  shown  at  B  and  C,  it  will  appear  to  pass  either  above  or  below  the  Sun,  as  shown  at 
D  and  E. 

For  the  relative  position  of  the  planets'  orbits,  and  their  inclination  to  the  plane  of  the 
ecliptic,  see  1,  of  the  Atlas.  Here  the  dotted  lines  continued  from  the  dark  lines, 
denote  the  inclination  of  the  orbits  to  the  plane  of  the  ecliptic,  which  inclination  is 
marked  in  figures  on  them.  Let  the  student  fancy  as  many  circular  pieces  of  paper 
intersecting  each  other  at  the  several  angles  of  inclination  marked  on  the  Map,  and  be 
will  be  enabled  to  understand  more  easily  what  is  meant  by  the  "  inclination  of  the 
planets'  orbits." 

348.  Being  commonly  immersed  in  the  Sun's  rays  in  the  even- 
ing, and  thus  continuing  invisible  till  it  emerges  from  them  in 
the  morning,  Mercury  appeared  to  the  ancients  like  two  distinct 
stars.  A  long  series  of  observations  was  requisite,  before  they 

846.  When  may  Mercury  be  seen?  Why  not  at  other  times?  How  far  does  it  depart 
from  the  Sun  on  either  side?  What  is  meant  by  the  elongation  of  a  planet  ?  Its  aphe- 
lion and  perihelion  f  347.  In  what  direction  do  the  planets  revolve  around  the  Sun  ? 
What  is  the  apparent  motion  of  Mercury?  Do  they  ever  cross  the  Sun's  disc?  Wvf 
aot  at  every  revolution?  848.  How  svas  Mercury  regarded  by  the  ancients? 


180 


ASTRONOMY. 


recognized  the  identity  of  the  star  which  was  seen  to  recede 
from  the  Sun  in  the  morning  with  that  which  approached  it  it 
the  evening.  But  as  the  one  was  never  seen  until  the  other 
disappeared,  both  were  at  last  found  to  be  the  same  planet,  which 
thus  oscillated  on  each  side  of  the  Sun. 

349.  Mercury's  oscillation  from  west  to  east,  or  from  east  to 
west,  is  really  accomplished  in  just  half  the  time  of  its  revolution, 
which  is  about  44  days  ;  but  as  the  Earth,  in  the  mean  time, 
follows  the  Sun  in  the  same  direction,  the  apparent  elongations 
will  be  prolonged  to  between  55  and  65  days. 

350.  The  passage  of  Mercury  or  Venus  directly  between  the 
Earth  and  the  Sun,  and  apparently  over  this  disc,  is  called  a 
Transi*.     A  transit  can  never  occur  except  when  the  interior 
planet  is  in  or  very  near  the  ecliptic.     The  Earth* and  the  planet 
must  be  on  the  same  side  of  the  ecliptic  ;  the  planet  being  at. 
one  of  its  nodes,  and  the  Earth  on  the  line  of  its  nodes. 


This  cut  represents  the  ecliptic  and  zodiac1,  with  the  orbit  of  an  interior  planet,  hia 
node*,  &c.  Tht  line  of  his  nodes  is,  as  shown,  in  the  16"  of  8  and  the  16°  of  Tit.  Now  if 
the  earth  is  in  e  ,  on  the  line  L  N,  as  shown  in  the  cut,  when  Mercury  is  at  his  ascending 
node  (ft),  he  will  seem  to  pass  upward  over  the  Sun's  face,  like  a  dark  spot,  as  repre- 
sented in  the  figure.  On  the  other  hand,  if  Mercury  is  at  his  descending  node  ($), 
when  the  earth  is  in  the  16*  of  TTJ,,  the  former  will  seem  to  pass  downward  across  the 
dive  of  the  Sun. 

351.  As  the  nodes  of  his  orbit  are  on  opposite  sides  of  the 
ecliptic,  and  are  passed  by  the  Earth  in  May  and  November,  it 
follows  that  all  transits  of  Mercury  must  occur  in  one  or  the 
other  of  these  months.  They  are,  therefore,  called  the  Node 
months.  As  is  shown  in  the  diagram,  the  Earth  passes  the 

849.  In  what  time  is  the  oscillation  of  Mercury  from  east  to  west  really  accomplUhf-iV 
Wh:it  is  the  apparent  time,  and  why?  350.  What  is  a  transit  T  When  do  they  occur  rt 
What  are  the  nod,'*  of  a  planet's  orbit?  The  tine  of  the  node*  851.  What  ur«  the 


THE    PR,  MARY    PLANETS MERCURY    AND    VENUS.       181 


TOAKSITS  OP  MBROUBT. 
NORTH 


ascending  Node  of  Mercury  in  November,  and  the  descending  in 
May  ;  the  former  of  which  is  in  the  16th  degree  of  Taurus,  and 
the  latter  in  the  16th  degree  of  Scorpio. 

All  the  transits  of  Mercury  ever  noticed  have  occurred  in  one  or  the  other  of  thcco 
months,  and  for  the  reason  already  assigned.  The  first  ever  observed  took  place  Novem- 
ber 6, 1631 ;  since  which  time  there  have  been  29  others  by  the  same  planet— in  all  80— 
8  in  May,  and  22  in  November. 

352.  The  last  transit  of  Mercury  occurred  November  11,  1861 ; 
and  the  next  will  take  place  November  4,  1868.     Besides  this, 
there  will  be  four  more  during  the  present  century — two  in  May, 
and  two  in  November. 

The  accompanying  cut  is  a  de- 
lineation of  all  the  transits  of  Mer- 
cury from  1802  to  the  close  of  the 
present  century.  The  dark  line 
running  east  and  west  across  the 
Sun's  center  represents  the  plane 
of  the  ecliptic,  and  the  dotted  lines 
the  apparent  paths  of  Mercury  in 
the  several  transits.  The  planet 
is  shown  at  its  nearest  point  to  the 
Sun's  center.  Its  path  in  the  last 
transit  and  in  the  next  will  easily 
be  found. 

The  last  transit  of  Mercury  was 
observed  in  this  country  by  Pro- 
fessor Mitchel,  at  the  Cincinnati 
Observatory,  and  by  many  others 
both  in  America  and  in  Europe. 
The  editor  had  made  all  necessary 
preparation  for  observing  the  phe- 
nomenon at  his  residence,  near 
Oswego,  New  York  ;  but,  unfor- 
tunately, his  sky  was  overhung 
with  clouds,  which  hid  the  sun 
from  his  view,  and  disappointed  all 
his  hopes. 

353.  By  comparing  the  mean  motion  of  any  of  the  planets 
with  the  mean  motion  of  the  Earth,  we  may  readily  determine 
the  periods  in  which  they  will  return  to  the  same  points  of  their 
orbit,  and  the  same  positions  with  respect  to  the  Sun.     The 
knowledge  of  these  periods  will  enable  us  to  determine  the  hour 
when  the  planets  rise,  set,  and  pass  the  meridian,  and  in  general 
all  the  phenomena  dependent  upon  the  relative  position  of  the 
Earth,  the  planet  and  the  Sun  ;  for  at  the  end  of  one  of  these 
periods  they  commence  again,  and  all  recur  in  the  same  order. 

We  have  only  to  find  a  number  of  sidereal  years,  in.  which  the  planet  completes 
exactly,  or  very  nearly,  a  certain  number  of  revolutions;  that  is,  to  find  such  a  number 
if  planetary  revolutions,  as,  when  taken  together,  shall  be  exactly  equal  to  one,  or  any 
lumber  of  revolutions  of  the  Earth.  In  the  case  of  Mercury  this  ratio  will  be  as  87.909 
s  to  365.256.  Whence  find  that, 


SOUTH 


node  montlm  of  a  planet?  The  node  months  of  Mercury?  352.  When  did  the  last 
transit  of  Mercury  occur?  When  will  the  next  take  place?  What  ethers  during  the 
present  century?  What  said  of  the  last  transit  of  Mercury  ?  353.  How  may  we  deter- 
•aius  when  'rj'iiH'-s  will  occur?  What  ratio  is  found  between  the  revolutions  of  Mercury 


182 


ASTRONOMY. 


7  periodical  revolutions  of  the  Earth  are  equal  to  29  of  Mercury  - 
18  periodical  revolutions  of  the  Earth  are  equal  to  54  of  Mercury : 
33  periodical  revolutions  of  the  Earth  are  equal  to  137  of  Mercury : 
46  periodical  revolutions  of  the  Earth  are  equal  to  191  of  Mercury. 

Therefore,  transits  of  Mercury,  at  the  same  node,  may  happen  at  intervals  of  7,  13-,  33, 46-. 

<kc.  years.     Transits  of  Venus,  as  well  as  eclipses  of  the  Sun  and  Moon,  are  calculated 

upon  the  same  principle. 
The  following  is  a  list  of  all  the  Transits  of  Mercury  from  the  time  the  first  was  observotl 

by  Gassendi,  November  6,  1631,  to  the  end  of  the  present  century  : 


1631  Nov.  6. 
1644  Nov.  6. 
1651  Nov.  2. 
1661  May  3. 
1664  Nov.  4. 
1674  May  6. 
1677  Nov.  7. 
1690  Nov.  9. 
1697  Nov.  2. 

1707  May  5. 
1710  Nov.  6. 
1723  Nov.  9. 
1736  Nov.  10. 
1740  Nov.  2. 
1743  Nov.  4. 
1753  May  5. 
1756  Nov.  6. 
1769  Nov.  9. 

1776  Nov.  2. 
1782  Nov.  12. 
1786  May  3. 
1789  Nov.  5. 
1799  May  7. 
1802  Nov.  8. 
1815  Nov.  11. 
1822  Nov.  4. 
1832  May  5. 

1835  Nov.  7. 
1845  May  8 
1848  Nov.  9. 
1861  Nov.  11. 
1868  Nov.  4. 
1878  May  6. 
1881  Nov.  7. 
1891  May  9. 
1894  Nov.  10. 

354.  The  sidereal  revolution  of  a  planet  respects  its  absolute 
motion  ;  and  is  measured  by  the  time  the  planet  takes  to  revolve 
from  any  fixed  star  to  the  same  star  again.     The  synodical  revo- 
lution of  a  planet  respects  its  relative  motion  ;  and  is  measured 
by  the  time  that  a  planet  occupies  in  coming  back  to  the  same 
position  with  respect  to  the  Earth  and  the  Sun. 

SIDEREAL  AXD  SYNODIC    BEVOLUTIOM3. 

In  the  adjoining  cut  the  revolution  of 

..--""  """-..  the  Earth    from  A,  opposite  the  star  B, 

around  to  the  same  point  again,  would  be 
a  sidereal  revolution. 

Suppose  the  Earth  and  Mercury  to  start 
together  from  the  points  A  C  (where  Mer- 
cury would  be  in  inferior  conjunction  with 
the  Sun),  and  to  proceed  in  the  direction 
of  the  arrows.  In  88  days  Mercury  would 
come  around  to  the  same  point  again ; 
but  as  the  Earth  requires  more  than  four 
times  that  number  of  days  for  a  revolu- 
tion, she  will  only  have  reached  the  point 
D  when  Mercury  arrives  at  C  again  ;  so 
that  they  will  not  be  in  conjunction,  and  a 
synodic  revolution  will  not  be  completed 
by  Mercury.  He  starts  on,  however,  in 
his  second  round,  and  constantly  gaining 
upon  the  Earth,  till  in  27  days  from  the 
time  he  left  C  the  second  time,  he  over- 
takes the  Earth  at  E  and  F,  and  is  again  in 
inferior  conjunction. 

from  this  illustration,  it  will  be  seen  that  the  synodic  revolution  of  a  planet  must 
always  require  more  time  than  the  sidereal. 

355.  The  absolute  motion  of  Mercury  in  its  orbit  is  109,157 
miles  an  hour  ;  that  of  the  Earth  is  68,288   miles  ;  the  differ- 
ence, 41,469  miles,  is  the  mean  relative  motion  of  Mercury,  with 
respect  to  the  Earth. 

The  sidereal  revolution  of  Mercury  is  87d.  23h.  15m.  44s.    Its  synodical  revolution  ie 


and  the  Earth?  354.  What  is  a  sidereal  revolution  of  a  planet?  A  synodic.alY 
855.  What  is  the  absolute  motion  of  Mercury  in  his  orbit?  What  is  that  of  the  Earth? 
The  difference,  or  relative  motion  of  Mercury?  What  is  his  sidereal  period?  His 
uynoditi  t  II  .T  is  the  latter  ascertained? 


THE    PRIMARY    PLANETS MERCURY    AND    VENUS.       183 

found  by  dividing  the  wh<  fe  circumference  of  360°  by  its  relative  motion  in  respect  to  the 
tearth.  Thus,  the  mean  daily  motion  of  Mercury  is  14782" .565;  that  of  the  Earth  is 
8548". 318  ;  and  their  difference  is  11184'. 237,  being  Mercury's  relative  motion,  or  what  it 
gains  on  the  Earth  every  day.  Now  by  simple  proportion,  11184".237  is  to  1  day,  as  360* 
is  to  115d.  21h.  8',  24",  the  period  of  a  synodical  revolution  of  Mercury. 


VENUS. 

356.  There  are  but  few  persons  who  have  not  observed  a 
beautiful  star  in  the  west,  a  little  after  sunset,  call  the  evening 
star.     This  star  is  Venus.     It  is  the  second  planet  from  the 
Sun.     It  is  the  brightest  star  in  the  firmament,  and  on  this 
account  easily  distinguished  from  the  other  planets. 

If  we  observe  this  planet  for  several  days,  we  shall  find  that 
it  does  not  remain  constantly  at  the  same  distance  from  the  Sun, 
but  that  it  appears  to  approach,  or  recede  from  him,  at  the  rate 
of  about  three-fifths  of  a  degree  every  day  ;  and  that  it  is  some- 
times on  the  east  side  of  him,  and  sometimes  on  the  west,  thus 
continually  oscillating  backwards  and  forwards  between  certain 
limits. 

357.  As  Venus  never  departs  quite  48°  from  the  Sun,  it  is 
never  seen  at  midnight,  nor  in  opposition  to  that  luminary  ; 
being  visible  only  about  three  hours  after  sunset,  and  as  long 
before  sunrise,  according  as  its  right  ascension  is  greater  or  less 
than  that  of  the  Sun.     At  first,  we  behold  it  only  a  few  minutes 
after  sunset ;  the  next  evening  we  hardly  discover  any  sensible 
change  in  its  position  ;  but  after  a  few  days,  we  perceive  that 
it  has  fallen  considerably  behind  the  Sun,  and  that  it  continues 
to  depart  farther  and  farther  from  him,  setting  later  and  later 
every  evening,  until  the  distance  between  it  and  the  Sun  is 
equal  to  a  little  more  than  half  the  space  from  the  horizon  to  the 
zenith,  or  about  46°.     It  now  begins  to  return  toward  the  Sun, 
making  the  same  daily  progress  that  it  did  in  separating  from 
him,  and  to  set  earlier  and  earlier  every  succeeding  evening, 
until  it  finally  sets  with  the  Sun,  and  is  lost  in  the  splendor  of 
his  light. 

358.  A  few  days  after  the  phenomena  we  have  now  described, 
we  perceive,  in  the  morning,  near  the  eastern  horizon,  a  bright 
star  which  was  not  visible  before.     This  also  is  Venus,  which  is 
now  called  the  morning  star.     It  departs  farther  and  farther 
from  the  Sun,  rising  a  little  earlier  every  day,  until  it  is  seen 

856.  Describe  Venus.  What  called?  Distance  from  the  Sun ?  What  change  of  posi- 
tion observable  ?  357.  Greatest  distance  to  which  she  departs  from  the  Sun?  What 
Consequence'  How  and  when  seen?  358.  What  next  after  these  phenomena? 


184  ASTRONOMY. 

about  46°  west  of  him,  where  it  appears  stationary  for  a  few 
days  ;  then  it  resumes  its  course  towards  the  Sun,  appearing 
later  and  later  every  morning,  until  it  rises  with  the  Sun,  and 
we  cease  to  behold  it.  In  a  few  days,  the  evening  star  again 
appears  in  the  west,  very  near  the  setting  sun,  and  the  same 
phenomena  are  again  exhibited.  Such  are  the  visible  appear- 
ances of  Yenus. 

359.  Yenus  revolves  about  the  Sun  from  west  to  east  in  224 1 
days,  at  the  distance  of  about  69,000,000  of  miles,  moving  in 
her  orbit  at  the  rate  of  80,000  miles  an  hour.      She  turns 
around  on  her  axis  once  in  23  hoars,  21  minutes,  and  7  seconds. 
Thus  her  day  is  about  25  minutes  shorter  than  ours,  while  her 
year  is  equal  to  7£  of  our  months,  or  32  weeks. 

360.  The  mean  distance  of  the  Earth  from  the  Sun  is  estimated 
at  95,000,000  of  miles,  and  that  of  Yenus  being  69,000,000, 
the  diameter  of  the  Sun,  as  seen  from  Yenus,  will  be  to  his 
diameter  as  seen  from  the  Earth,  as  95  to  69,  and  the  surface 
of  his  disc  as  the  square  of  95  to  the  square  of  69,  that  is, 
as  9025  to  4761,  or  as  2  to  1,  nearly.     The  intensity  of  light 
and  heat  being  inversely  as  the  square  of  their  distances  from 
the  Sun  (No.  342),  Yeuus  receives  twice  as  much  light  and  heat 
as  the  Earth. 

361.  The  orbit  of  Yenus  is  within  the  orbit  of  the  Earth  ; 
for  if  it  were  not,  she  would  be  seen  as  often  in  opposition  to  the 
Sun,  as  in  conjunction  with  him  ;  but  she  was  never  seen  rising 
in  the  east  while  the  Sun  was  setting  in  the  west.     Nor  was  she 
ever  seen  in  quadrature,  or  on  the  meridian,  when  the  Sun  was 
either  rising  or  setting.     Mercury's  greatest  elongation  being 
about  23°  from  the  Sun,  and  that  of  Yenus  about  46°,  the  orbit 
of  Yenus  must  be  outside  of  the  orbit  of  Mercury. 

362.  The  diameter  of  Yenus  is  about  7.900  miles ;  bnt,  her 
apparent  diameter  and  brightness  are  constantly  varying,  accord- 
ing to   her  distance   from  the  Earth.     When  Yenus   and   tho 
Earth  are  on  the  same  side  of  the  Sun,  her  distance  from  tho 
Earth  is  only  26,000,000  of  miles  ;  when  they  are  on  opposite 
sides  of  the  Sun,  her  distance  is   164,000,000  of  miles.     Were 
the  whole  of  her   enlightened  hemisphere   turned   towards  us, 
when  she  is  nearest,  she  would  exhibit  a  light  and  brilliancy 

859.  What  is  Venus'  sidereal  period  ?     Distance  from  the  Sun  ?     Rate  of  motion 
Time  of  rotation  upon  her  axis?     How,  then,  do  her  day  and  year  compare  with  ours? 
800.  How  must  the  Sun  appear  from   Venus,  and  why?     What  of  her  light  and   heat? 
861-  Where  .8  the  orbit  of  Venus  situated?     What  proof  of  this?        362.  Venus'  diame- 
ter ?     lljr  apparent  diameter?    State  her  least  and  greatest  distances  from  the  Earth 


THE    PRIMARY    PLANETS MERCURY    AND    VENUS.        185 


twenty-five  times  greater  than  she  generally  does,  and  appear 
like  a  smaU  brilliant  moon  ;  but,  at  that  time,  her  dark  hemi- 
sphere is  turned  towards  the  Earth. 

When  Venu_  approaches  nearest  to  the  Earth,  her  apparent,  or  observed  diameter  iu 
61".2;  when  most  remote,  it  is  only  9". 6  ;  now  61".2-»-9*.6=6?i.  hence  when  nearest  the 
Earth  her  apparent  diameter  is  G3,  times  greater  than  when  most  distant,  and  surface 
of  her  disc  (£/t°)-  or  nearly  41  times  greater.  In  this  work,  the  apparent  size  of  the 
heavenly  bodies  is  estimated  from  the  apparent  surface  of  their  discs,  which  is  always 
proportional  to  the  squares  of  their  apparent  diameters. 

363.  Mercury  and  Venus  are  called  Interior  planets,  because 
their  orbits  are  within  the  Earth's  orbit,  or  between  it  and  the 
Sun.  The  other  planets  are  denominated  Exterior,  because  their 
orbits  are  without  or  beyond  the  orbit  of  the  Earth.  (Map  I.) 
As  the  orbits  of  Mercury  and  Venus  lie  within  the  Earth's  orbit, 
it  is  plain,  that  once  in  every  synodical  revolution,  each  of  these 
planets  will  be  in  conjunction  on  the  same  side  of  the  Sun.  In 
the  former  case,  the  planet  is  said  to  be  in  its  inferior  conjunc- 
tion, and  in  the  latter  case,  in  its  superior  conjunction  ;  as  in  the 
following  figure. 


MARS    IN    CONJUNCTION 

e-   ... 

<5  "•-, 


Let  the  student  imagine  him- 
self stationed  upon  the  earth  in 
the  cut.  Then  the  sun  and  three 
planets  above  are  in  conjunc- 
tion. The  inferior  and  supe- 
rior are  distinguished ;  while  at 
A,  a  planet  is  shown  in  quadra- 
ture, and  at  the  bottom  of  the 
cut  the  planet  Mars  in  opposi- 
tion with  the  sun  and  interior 
planet. 

The  period  of  Venus'  synodi- 
cal revolution  is  found  in  the 
same  manner  as  that  of  Mer- 
cury ;  namely,  by  dividing  the 
whole  circumference  of  her  orbit 
by  her  mean  relative  motion  in 
a  day.  Thus,  Venus'  abnolitte 
mean  daily  motion  is  1°  36'  7'.8, 
the  Earth's  is  59'  8'.3,  and  theii 
difference  it,  36'  W.5.  Divide 
860°  by  86'  59".5,  and  it  gives 
583.920,  or  nearly  584  days  for 
Venus'  synodical  revolution,  or 
the  period  in  which  she  is 
twice  in  conjunction  with  the 
MARS  IN  "OPPOSITION  Earth. 

364  When  Venus'  right  ascension  is  less  than  that  of  the 
Sun,  she  rises  before  him  ;  when  greater,  she  appears  after  his 
setting.  She  continues  alternately  morning  and  evening  star, 
for  a  period  of  292  days,  each  time. 

How  would  she  appear  if  we  saw  her  enlightened  side  when  nearest  to  us?  What  com- 
putation in  the  fine  print?  363.  How  are  Mercury  and  Venus  distinguished,  and  why  ? 
What  said  of  conjunctions  !  Describe  the  inferior  and  superior  ?  How  is  the  period  of 
Venus'  synodical  revolution  found »  3G4.  When  is  Venus  evening  star  »  Morningy 


186  ^STKONOMY. 

To  those  "vho  are  but  little  acquainted  with  astronomy,  it  will  seem  strange,  at  first, 
that  Venus  nhould  apparently  continue  longer  on  the  east  or  west  side  of  the  Sun,  than 
the  whole  time  of  her  periodical  revolution  around  him.  But  it  will  be  easily  understood, 
when  it  is  considered,  that  while  Venus  moves  around  the  Sun,  at  the  rate  of  about  1*  36' 
of  angular  motion  per  day,  the  Earth  follows  at  the  rate  of  59' ;  so  that  Venus  actually 
gains  on  the  Earth,  only  87'  in  a  day. 

Now  it  is  evident  that  both  planets  will  appear  to  keep  on  the  same  side  of  the  Sun, 
until  Venus  has  gained  half  her  orbit,  or  180°  in  advance  of  the  Earth ;  and  this,  at  a 
mean  rate,  will  require  292  days,  since  292  x  37' =10804',  or  180°  nearly. 

365.  Terms  passes  from  her  inferior  to  her  superior  conjunc- 
tion in  about  292  days.     At  her  inferior  conjunction,  she  is 
26,000,000  of  miles  from  the  Earth  ;  at  her  superior  conjunc- 
tion, 164,000,000  of  miles.     It  might  be  expected  that  her  bril- 
liancy would  be  proportionally  increased,  in  the  one  case,  and 
diminished  in  the  other  ;  and  so  it  would  be,  were  it  not  that 
her  enlightened  hemisphere  is  turned  more  and  more  from  us,  as 
she  approaches  the  Earth,  and  comes  more  and  more  into  view 
as  she  recedes  from  it.     It  is  to  this  cause  alone  that  we  must 
attribute  the  uniformity  of  her  splendor,  as  it  usually  appears  to 
the  naked  eye. 

366.  Mercury   and  Venus   present   to   us,   successively,   the 
various   shapes   and   appearances   of  the  Moon  ;    waxing  and 
waning  through  different  phases,  as  shown  in  the  following  cut, 
from  the  beautiful  crescent  to  the  full  rounded  orb.     This  fact 
shows,  that  they  revolve  around  the  Sun,  and  between  the  Sun 
and  the  Earth. 

PHASES  OF  VEXUS  AS  SHE  REVOLVES  ARODHD  TES  SUK. 


It  should  be  remarked,  however,  that  Venus  is  never  seem,  when  she  is  entirely  full., 
except  once  or  twice  in  a  century,  when  she  passes  directly  over  the  Sun's  disc.  At 
every  other  conjunction,  she  is  either  behind  the  Sun,  or  so  near  him  as  to  be  hidden  by 
tlie  splendor  of  his  light.  The  preceding  diagram  better  illustrates  the  various  appear- 
ances of  Venus,  as  she  moves  around  the  Sun,  than  any  description  of  them  could  do. 

367.  From  her  inferior  to  her  superior  conjunction,  Venus, 
appears  on  the  west  side  of  the  Sun,  and  is  then  our  morning 


How  long  each?  How  is  it  that  Venus  is  east  ur  west  of  the  Sun  292  days,  when  her 
periodic  revolution  is  performed  in  about  '225  days  ?  365.  What  is  the  time  from  one 
;onjunction  of  Venus  to  another?  Is  her  brilliancy  in  proportion  to  her  nearness?  Why 
.lot?  366.  What  phases  do  Mercury  and  Venus  exhibit,  and  what  do  they  prove? 
/Vr<.'  they  ever  soon  entirely  full  t  367.  When  is  Veiius  morning  star?  When  evening? 


THE    PRIMARY    PLANETS  -  MERCURY    AND    VENUS.         187 

star  ;  from  her  superior  to  her  inferior  conjunction  she  appears 
on  the  east  side  of  the  Sun,  and  is  then  our  evening  star.  These 
phenomena  are  illustrated  by  the  following  diagram. 


TESCS  AS  MORNING  AND  EVENING  STAIl. 


Let  the  student  hold  the  book  up  south  of  him,  and  he  will  at  once  Bee  why  Venus  is 
alternately  morning  and  evening  star.  Let  the  plane  A  B  represent  tlio  sensible  or  visi- 
ble horizon,  C  D  the  apparent  daily  path  of  the  Sun  through  the  heavens,  and  E  the 
Earth  in  her  apparent  position.  The  Sun  is  shown  at  three  different  points — namely, 
rising  in  the  east,  on  the  meridian,  and  setting  in  the  west;  while  Venus  is  seen  revolving 
around  him  from  west  to  east,  or  in  the  direction  of  the  arrows.  Now  it  is  obvious  that 
when  Venus  is  at  F,  or  west  of  the  Sun,  she  sets  before  him  as  at  G,  and  rises  before  him 
as  at  H.  She  must,  therefore,  be  morning  star.  On  the  other  hand,  when  she  is  ea-nt 
of  the  Sun,  as  at  J,  she  lingers  in  the  west  after  the  Sun  has  gone  down,  as  at  K,  and  is 
consequently  evening  star. 

In  this  cut,  Venus  would  be  at  her  greatest  elongation  eastward  at  J,  and  westward 
at  F,  and  in  both  cases  would  be  "stationary."  At  L  and  M  she  would  be  in  conjunc- 
tion with  the  Sun. 

Were  the  earth  to  suspend  her  daily  rotation,  with  the  Sun  on  the  meridian  of  the 
observer,  as  represented  at  L,  we  might  readily  watch  Venus  through  her  whole  circuit 
around  the  Sun. 

368.  Like  Mercury,  Yenus  sometimes  seems  to  be  stationary. 
Her  apparent  motion,  like  his,  is  sometimes  rapid  ;  at  one  time, 
direct,  and  at  another,  retrograde. ;  vibrating  alternately  back- 
wards and  forwards,  from  west  to  east,  and  from  east  to  west. 
These  vibrations  appear  to  extend  from  45°  to  41°,  on  each  side 
of  the  Sun. 

Consequently  she  never  appears  in  the  eastern  horizon  more  than  three  hours  before 
sunrise,  nor  continues  \onger  in  the  western  horizon  after  sunset.  Any  star  or  planet 
therefore,  however  brilliant  it  may  appear,  which  is  seen  earlier  or  later  than  this,  cannot 
be  Venus. 

369.  In  passing  from  her  western  to  her  eastern  elongation, 

268.  Is  she  ever  stationary?  What  other  irregularities  in  her  apparent  motion? 
SCO.  When  is  her  motion  direct?  When  retrograde?  When  most  rapid?  When 


188 


ASTRONOMY. 


her  motion  is  from  west  to  east,  in  the  order  of  the  signs  ;  it  is 
thence  called  direct  motion.  In  passing  from  her  eastern  to  her 
western  elongation,  her  motion  with  respect  to  the  Earth  is 
from  east  to  west,  contrary  to  the  order  of  the  signs  ;  it  is 
thence  denominated  retrograde  motion.  Her  motion  appears 
quickest  about  the  time  of  her  conjunctions  ;  and  she  seems  sta- 
tionary at  her  elongations.  She  is  brightest  about  thirty-six 
days  before  and  after  her  inferior  conjunction,  when  her  light  is 
so  great  as  to  project  a  visible  shadow  in  the  night,  and  some- 
times she  may  be  seen  with  the  naked  eye  even  at  noon-day. 

DIKKCT  .iND  RCTROGIIADK    KOTIOHS. 

The  cause  of  the  apparent  re- 
trogression  of  the  interior  planets 
is  the  fact  that  they  revolve  much 
more  rapidly  than  the  earth,  from 
which  we  view  them ;  causing 
their  direct  motion  to  appear  to 
be  retrograde. 

Suppose  the  earth  to  be  at  A,  and  Venus  at 
B,  she  would  appear  to  be  at  C,  among  the 
stars.  If  the  earth  remained  at  A  while 
Venus  was  passing  from  B  to  D,  she  would 
seem  to  retrograde  from  C  to  E;  but  as  the 
earth  passes  from  A  to  F  while  Venus  goei 
from  B  to  D,  Venus  will  appear  to  be  at  G ; 
and  the  amount  of  her  apparent  westward 
motion  will  only  be  from  C  to  G, 

370.  If  the  orbit  of  Yenus  lay 
exactly  in  the  plane  of  the  Earth's 
orbit,  she  would  pass  centrally 
across  the  Sun's  disc,  like  a  dark 
round  spot,  at  every  inferior  conjunction ;  but,  as  one-half 
of  her  orbit  lies  about  3i°  above  the  ecliptic,  and  the  other  half 
as  far  below  it,  she  will  always  pass  the  Sun  a  very  little  above 
or  below  it,  except  when  her  inferior  conjunction  happens  in,  or 
near  one  of  her  nodes  ;  in  which  case  she  will  make  a  transit. 
(See  cuts,  pages  179  and  180.) 

This  phenomenon,  therefore,  is  of  very  rare  occurrence  ;  it  can 
happen  only  twice  in  a  century  ;  because  it  is  only  twice  in  that 
time  that  any  number  of  complete  revolutions  of  Venus  are  just 
or  nearly  equal  to  a  certain  number  of  the  Earth's  revolutions. 

The  principle  which  was  illustrated  in  predicting  the  transits  of  Mercury,  applioa 
equally  well  to  those  of  Venus  ;  that  is,  we  must  find  such  sets  of  numbers  (representing 

orightest?  State  the  cause  of  the  apparent  retrograde  motion?  870.  Why  have  we  not 
•i  transit  at  every  revolution  of  Venus?  How  frequent,  therefore?  Uow  predicted  I 
When  do  her  nodes  cut  the  ecliptic? 


THE    PR  MARY    PLANETS  -  MERCURY    AND    VENUS.       180 

complete  revolutions  of  the  Earth  and  Venus)  as  shall  be  to  each  other  in  the  ratio  cf 
tL«ir  periodical  times,  or  as  3'55.256  is  to  2'24.7.  Thus  :  the  motion  of  Venus,  in  the  Julian 
pears,  is  21t;6691'.52  ;  that  of  the  Earth  for  the  same  period  being  129G27'.45,  the  ratio 
will  be  ^Sr^'Vy  *'^f-  As  tne  *wo  terms  of  this  fraction  cannot  be  reduced  by  a  com 
inon  divisor,  we  must  multiply  them  by  such  numbers  as  will  make  one  a  multiple  of  the 
other;  accordingly,  13  times  the  denominator  will  be  nearly  equal  to  8  times  the  nume- 
rator ;  and  475  times  the  der^^minator  will  equal  291  times  the  numerator. 

By  combining  these  two  periods  and  their  multiples  by  addition  and  subtraction,  wo 
shall  obtain  tlie  period  of  all  the  transits  that  have  ever  happened.  Thus  :  291—8  x  7=235, 
another  period  ;  and  291—6  x  8=243,  another  period,  and  so  on.  "  Whence  we  find  that 

8  periodical  revolutions  of  the  Earth  are  equal  to  13  of  Venus: 
235  periodical  revolutions  of  the  Earth  are  equal  to  382  of  Venus  : 
243  periodical  revolutions  of  the  Earth  are  equal  to  395  of  Venus: 
251  periodical  revolutions  of  the  Earth  are  equal  to  4(>S  of  Venus  : 
291  periodical  revolutions  of  the  Earth  are  equal  to  475  of  Venus. 

Hence  a  transit  of  Venus  may  happen  at  the  same  node,  after  an  interval  of  8  years, 
but  if  it  do  not  happen  then,  it  cannot  take  place  again  at  the  same  node,  in  less  than 
235  years.  The  orbit  of  Venus  crosses  the  ecliptic  near  the  middle  of  Gemini  and  Sagit- 
tarius; and  those  points  mark  the  position  of  her  nodes.  At  present,  her  ascending  node 
is  in  the  14th  degree  of  Gemaii,  and  her  descending  node  in  the  same  degree  of  S-'.git- 
tarius. 

371.  The  node  months  of  Yenus  are  December  and  Jane. 
The  line  of  her  nodes  lies  in  Gemini  (  n  )  and  Sagittarius  (  £  )  ; 
and  as  the  Earth  always  passes  those  points  in  the  months 
named,  it  follows  that  all  transits  of  Yenus  must  occur  in  those 
mouths  for  ages  to  come. 

for  as  tho 
will  reach 

that  point  in  the  ecliptic  in  one  month  after  she  passes  the  line  of  Mercury's  nodes;  so 
that  if  his  transits  occur  iuMay  and  November,  hers  should  occur  in  June  and  December, 
as  is  always  the  case. 

272.  The  first  transit  ever  known  to  have  been  seen  by  any 
human  being,  took  place  at  the  ascending  node,  December  4th, 
1639.*  If  to  this  date  we  add  235  years,  we  shall  have  the 

*  This  phenomenon  was  first  witnessed  by  Horrox,  a  young  gentleman  about  21  years 
of  age,  living  in  an  obscure  village  15  miles  north  of  Liverpool.  The  tables  of  Kepler, 
constructed  upon  the  observations  of  Tycho  Brahe,  indicated  a  transit  of  Venus  in  1631, 
but  none  was  observed.  Horrox,  without  much  assistance  from  books  and  instruments, 
set  himself  to  inquire  into  the  error  of  the  tables,  and  found  that  such  a  phenomenon 
might  be  expected  to  happen  in  lb'39.  He  repeated  his  calculations  during  this  interval, 
with  all  the  carefulness  and  enthusiasm  of  a  scholar  ambitious  of  being  the  first  to  predict 
and  observe  a  celestial  phenomenon,  which,  from  the  creation  of  the  world,  had  never 
Deen  witnessed.  Confident  of  the  result,  he  communicated  his  expected  triumph  to  A 
confidential  friend  residing  in  Manchester,  and  desired  him  to  watch  for  the  event,  and 
to  take  observations.  So  anxious  was  Horrox  not  to  fail  of  witnessing  it  himself,  that  he 
commenced  his  observations  the  day  before  it  was  expected,  and  resumed  them  at  the 
rising  of  the  Sun  on  the  morrow.  Hut  the  very  Jiottr  when  his  calculations  led  him  to 
;xpect  the  visible  appearance  of  Venus  on  the  Sun's  disc,  wax  ttlxo  the  appointed  /tour 
for  the  public  wo».-ihip  of  God  on  the  Sabbatk.  The  delay  of  a  few  minutes  might 
dtprive  him  for  ever  of  an  opportunity  of  observing  the  transit.  If  its  very  commence- 
ment were  no*  noticed,  clouds  might  intervene,  and  conceal  it  until  the  Sun  should  set: 
a.  id  nearly  u.  century  and  a  half  would  elapse  before  another  opportunity  would  occur. 
He  had  been  waiting  for  the  event  with  the  most  ardent  anticipation  for  eight  years,  and 
the  result  premised  much  benefit  to  the  science.  JfoticWu&inding  oil  thi«,  Horroto 
twice  tfunpended  his  observations  and  twice  repaired  to  the  llou*e  of  God,  the  Great 
Author  of  the  bright  works  he  delighted  to  contemplate.  When  his  duty  was  thus  per- 

871.  Which  are  her  node  months  V        372.  When  was  the  first  transit  observed  '    What 

fmcrtsting  aiiecdo*cf 


This  proposition  will  be  well  understood  by  consulting  the  cut  on  page  oOft  ;  fo 
line  of  Venus'  nodes  is  only  one  sign  ahead  of  that  of  Mercury,  the  Earth  wi 


190  ASTRONOMY. 

time  of  the  next  transit  at  the  same  node,  which  will  accordingly 
happen  in  1874.  There  will  be  another  at  the  same  node  in 
1882,  eight  years  afterwards.  It  is  not  more  certain  that  this 
phenomenon  will  recur,  than  that  the  event  itself  will  engross 
the  attention  of  all  the  astronomers  then  living  upon  the  Earth. 
It  will  be  anticipated,  and  provided  for,  and  observed,  in  every 
inhabited  quarter  of  the  globe,  with  an  intensity  of  solicitude 
which  no  natural  phenomenon,  since  the  creation,  has  ever 
excited. 

373.  The  reason  why  a  transit  of  Yenus  should  excite  so  great 
an  interest  is,  because  it  may  be  expected  to  solve  an  important 
problem  in  astronomy,  which  has  never  yet  been  satisfactorily 
done  : — a  problem  whose  solution  will  make  known  to  us  the 
magnitudes  and  masses  of  all  the  planets,  the  true  dimensions  of 
their  orbits,  their  rates  of  motion  around  the  Sun,  and  their 
respective  distances  from  the  Sun,  and  from  each  other.     It  may 
be  expected,  in  short,  to  furnish  an  universal  standard  of  astro- 
nomical measure.     Another  consideration  will  render  the  obser- 
vation of  this  transit  peculiarly  favorable  ;  and  that  is,  astrono- 
mers will  be  supplied  with  better  instruments,  and  more  accurate 
means  of  observation,  than  on  any  former  occasion. 

So  important,  says  Sir  John  Herschel,  have  these  observations  appeared  to  astronomers, 
that  at  the  last  transit  of  Venus,  in  1769,  expeditions  were  fitted  out,  on  the  most  efficient 
scale,  by  the  British,  French,  Russian,  and  other  governments,  to  the  remotest  corners  of 
the  globe,  for  the  express  purpose  of  making  them.  The  celebrated  expedition  of  Captain 
Cook  to  Otaheite,  was  one  of  them.  The  general  result  of  all  the  observations  made  on 
this  most  memorable  occasion,  gives  8".5776  for  the  Sun's  horizontal  parallax. 

374.  The  phenomena  of  the  seasons  of  each  of  the  planets, 
like  those  of  the  Earth,  depend  upon  the  inclination  of  the  axis 
of  the  planet  to  the  plane  of  its  orbit,  and  its  revolution  around 
the  Sun.     The  inclination  of  the  axis  of  Yenus  to  the  plane  of 
her  orbit,  though  not  precisely  known,  io  commonly  estimated  at 
75°,  as  represented  to  the  eye  in  the  following  cut : 


rormed,  and  he  had  returned  to  his  chamber  the  second  time,  his  love  of  science  waa 
gratified  with  full  success ;  and  he  saw  what  no  mortal  eye  had  observed  before ! 

If  anything  can  add  interest  to  this  incident,  it  is  the  modesty  with  which  the  young 
astronomer  apologizes  to  tlie  world,  for  suspending  his  observations  at  all. 

"  I  observed  it,"  says  he,  "  from  sunrise  till  nine  o'clock,  again  a  little  before  ten,  and 
lastly  at  noon,  and  from  one  to  two  o'clock  ;  the  rest  of  the  day  being  devoted  to  highe" 
duties,  which  might  not  be  neglected  for  these  pastimes." 

When  the  next?  When  another?  How  will  it  be  regarded  ?  373.  Why  should  sucn 
an  event  excite  general  interest?  Remark  of  Sir  John  Herschel  ?  What  expedition  and 
what  results?  374.  Upon  what  do  the  s&^ons  of  the  planets  depend?  What  is  tho 
Inclination  of  Venus'  axi^  t<  the  piane  c  .er  orbit?  How  is  her  orbit  situated  vitli 
referent  to  the  ecliptic? 


THE    PRIMARY    PLANETS MERCURY    AN1»    VENUS.       191 

IMJUNATIOK  OF  TKNCS'  AXU. 


The  orbit  of  Venus  departs  from  the  ecliptic  8%',  while  her  oasis  is  inclined  to  the 
plane  of  her  orbit  75°,  as  shown  in  the  above  figure.  This  distinction  should  be  kept 
definitely  in  view  by  the  student. 

375.  The  declination  of  the  Sun  on  each  side  of  Venus'  equa- 
tor, must  be  equal  to  the  inclination  of  her  axis  :  and  if  this 
extends  to  75°,  her  tropics  are  only  15°  from  her  poles,  and  her 
polar  circles  only  15°  from  her  equator.     It  follows,  also,  that 
the  Sun  must  change  his  declination  more  in  one  day  at  Venus, 
than  in  five  days  on  the  Earth  ;  and,  consequently,  that  he  never 
shines  vertically  on  the  same  places  for  two  days  in  succession 
This  may,  perhaps,  be  providentially  ordered,  to  prevent  the  too 
great  effect  of  the  Sun's  heat,  which,  on  the  supposition  that  it 
is  in  inverse  proportion  to  the 'square  of  the  distance,  is  twice  as 
great  on  this  planet  as  it  is  on  the  Earth. 

376.  At  each  pole  of  Venus,  the  Sun  continues  half  of  her 
year  without  setting  in  summer,  and  as  long  without  rising  in 
winter ;  consequently,  her  polar  inhabitants,  like  those  of  the 
Earth,  have  only  one  day  and  one  night  in  the  year  ;  with  this 
difference,  that  the  polar  days  and  nights  of  Venus  are  not  quite 
two-thirds  as  long  as  ours. 

Between  her  polar  circles,  which  are  but  15°  from  her  equator, 
there  are  two  winters,  two  summers,  two  springs,  and  two 
autumns,  every  year.  But  because  the  Sun  stays  for  some  time 
near  the  tropics,  and  passes  so  quickly  over  the  equator,  the  win- 
ters in  that  zone  will  be  almost  twice  as  long  as  the  summers. 

The  north  pole  of  Venus'  axis  inclines  towards  the  20th 
degree  o*  Aquarius  ;  the  Earth's  towards  the  beginning  of  Can- 
cer ;  consequently,  the  northern  parts  of  Venus  have  summer 
in  the  signs  where  those  of  the  Earth  have  winter,  and  vice  versa. 

377.  When  viewed  through  a  good  telescope,  Venus  exhibits 
not  only  all  the  moon-like  phases  of  Mercury,  but  also  a  variety 
of  inequalities  on  her  surface  ;  dark  spots,  and  brilliant  shades, 
hills  and  valleys,  and  elevated  mountains.     But  on  account  of 

875.  What  is  the  amount  of  the  Sun's  declination  upon  Venus  ?  What  resu'ts  ?  What 
supposed  design  in  this  arrangement?  376.  What  said  of  the  polar  regions  of  Venus  V 
What  of  her  seasons  ?  How  is  her  north  pole  situated  with  respect  to  the  heftvcuu  ? 
What  consequence?  877.  Ilow  does  Venus  appear  through  a  telescope rj 


192  ASTRONOMY. 

the  great  density  of  her  atmosphere,  these  inequalities  arc  per- 
ceived with  more  difficulty  than*  those  upon  the  other  planeis. 


378.  The  mountains  of  Venus,  like  those  of  Mercury  and  tin 
Moon,  are  highest  in  the  southern  hemisphere.     According  to 
M.  Schroeter,  a  celebrated  German  astronomer,  who  spent  more 
than  ten  years  in  observations  upon  this  planet,  some  of  her 
mountains  rise  to  the  enormous  height  of  from  ten  to  twenty- 
two  miles.     The  observations  of  Dr.  Herschel  do  not  indicate  so 
great  an  altitude  ;  and  he  thinks,  th»t  in  general  they  are  con- 
siderably  overrated      He  estimates  the  diameter  of  Venus   at 
8649  miles  ;   making  her  bulk  more  than  one-sixth  larger  than 
that  of  the  Earth.     Several  eminent  astronomers  affirm,  that 
they  have  repeatedly  seen  Venus  attended  by  a  satellite,  and 
they  have  given  circumstantial  details  of  its  size  and  appearance, 
its  periodical  revolution  and  its  distance  from  her.     It  is  said  to 
resemble  our  Moon  in  its  phases,  its  distance,  and  its  magnitude. 
Other  astronomers  deny  the  existence  of  such  a  bcdy,  because 
it  was  not  seen  with  Venus  on  the  Sun's  disc,  at  the  transits  of 
1761  and  1769.     It  probably  does  not  exist. 

THE  EARTH. 

379.  The  Earth  is  the  place  from  which  all  our  observations 
of  the  heavenly  bodies  must  necessarily  be  made.     The  apparent 
motions  of  these  bodies  being  very  considerably  affected  by  her 
figure,  motions,  and  dimensions,  these  hold  an  important  place  in 
astronomical  science.     It  will,  therefore,  be  proper  to  consider, 
first,  some  of  the  methods  by  which  they  have  been  determined. 

If,  standing  on  the  sea-shore,  in  a  clear  day,  we  view  a  ship 
leaving  the  coast,  in  any  direction,  the  hull  or  body  of  the  vessel 

Why  less  distinct  than  the  other  planets?  37S.  Where  are  her  highest  monntalns 
Jituated?  Their  height?  Remark  <>f  Dr.  Herschel  ?  Hi*  estimate  of  Venus' diameter  ? 
What  said  about  a  satellite  around  Venus?  879.  Relation  of  the  earth  to  the  other 
planets  in  the  study  of  astronomy?  What  necessary,  therefore?  What  proof  of  the 
oonrexity  of  her  surface? 


THE  PRIMARY  PLANETS THE  EARTH. 


193 


6rst  disappears  ;  afterwards  the  rigging,  and  lastly  the  top  of 
the  mast  vanishes  from  our  sight. 


CONVEXITY  OP   TUB    HARTa'S   SCKt'ACh. 


Here  the  observer  upon  the  shore  at  A  sees  only  the  topmasts  of  the  ship,  whi.e  the 
man  standing  upon  the  pillar  at  B  sees  the  masts  and  sails,  and  part  of  the  hull.  Now, 
if  the  water  between  A  and  the  ship  were  exactly  flat  instead  of  convex,  the  vision  of  A 
tfould  extend  along  the  line  C,  and  he  could  see  the  whole  ship  as  well  as  B.  The  advan- 
'age  of  B  over  A,  in  consequence  of  his  elevation,  shows  that  the  surface  of  the  water 
is  convex  between  A  and  the  ship. 

380.  Again  :  navigators  have  sailed  quite  around  the  Earth, 
and  thus  proved  its  convexity. 

CONVEXITY  OF  THE  EARTH'S  SURFACE. 

Ferdinand  Magellan,  a  Portuguese,  was  the 
first  who  carried  this  enterprise  into  execution. 
He  embarked  from  Seville,  in  Spain,  and  directed 
his  course  towards  the  west.  After  a  long  voy- 
age, he  descried  the  continent  of  America.  Not 
finding  an  opening  to  enable  him  to  continue  his 
course  in  a  westerly  direction,  he  sailed  along  the 
coast  towards  the  south,  till,  coming  to  its  south- 
ern 3Xtremity,  he  sailed  around  it,  and  found 
himself  in  the  great  Southern  Ocean.  He  then 
resumed  his  course  towards  the  west.  After 
some  time  he  arrived  tit  the  Molucca  Islands,  in 
the  Eastern  IJemi#p?u>re ;  and  sailing  con- 
tinually towards  the  west,  he  made  Europe  from 
the  ea?t,  arriving  at  the  place  from  which  he 
set  out.* 

The  next  who  circumnavigated  the  Earth  wag 
Sir  Francis  Drake,  who  sailed  from  Plymouth, 
December  13,  15T7,  with  five  small  vessels,  and 
arrived  at  the  same  place,  September  26, 1580. 
Since  that  time,  the  circumnavigation  of  the  Earth  has  beeu  performed  by  Cavendish, 
Cordes,  Noort,  Sharten,  Heremites,  Dampier,  Woodes,  Rogers,  Schovten,  Roggewin,  Lord 
Anson,  Byron,  Carteret,  Wallis,  Bougainville,  Cook,  King,  Clerk,  Vancouver,  and  many 
others. 

381.  These   navigators,  by  sailing  in   a  westerly  direction, 
allowance  being  made  for  promontories,  &c.,  arrived  at  the  coun- 
try they  sailed  from.     Hence  the  Earth  must  be  either  cylindri- 
cal or  globular.     It  cannot  be  cylindrical,   because,  if  so,  the 
meridian  distances  would  all  be  equal  to  each  other,  which  is 

*  Magellan  sailed  from  Seville,  in  Spain,  August  10,  1519,  in  the  ship  called  the  Victory, 
accompanied  by  four  other  vessels.  In  April,  1521,  he  was  killed  in  a  skirmish  with  the 
natives,  at  the  island  of  Sehu,  or  Zfbu,  sometimes  called  Matan,  one  of  the  Philippines. 
One  of  his  vessels,  however,  arrived  at  St.  Lucar,  near  Seville,  September  7,  1522. 


880.  What  second  proof  stated  ?     Who  first  sailed  around  the  world?    Who  next? 
081.  In  what  direction  did  they  s.i'l?     How  did  these  voyages  prove  the  earth  to  he 


194 


ASTRONOMY. 


contrary  to  observation.     The  figure  of  the  Earth  is,  therefore, 
spherical. 

382.  The  convexity  of  the  Earth,  north  and  south,  is  proved 
by  the  variation  in  the  altitude  of  the  pole,  and  of  the  circum- 
polar  stars  ;  this  is  found  uniformly  to  increase  as  we  approach 
them,  and  to  diminish  as  we  recede  from  them. 

LATITUDE    FOUND  BY  THB  NORTH  STAR. 

Suppose  an  observer  standing 
upon  the  Earth,  and  viewing  the 
pole  star  from  the  46°  of  North 
latitude;  it  would,  of  course, 
appear  elevated  46°  above  hia 
visible  horizon.  But  let  him 
recede  southward,  and  as  he 
passed  over  a  degree  of  latitude, 
the  pole  star  would  settle  one 
degree  towards  the  horizon,  or 
more  properly,  his  northern 
horizon  would  be  elevated  one 
degree  towards  the  pole  star, 
till  at  length,  as  he  crossed  the 
equator,  the  North  star  wouk" 
sink  below  the  horizon,  and 
become  invisible.  Whence  wo  X 
derive  the  general  rule,  that 
the  alUtude  of  one  pole,  or  the 
depression  of  Vie  other,  at  any 
flaee  on  the  Earth's  wrface,  is  equal  to  the  latitude  of  that  place. 

383.  The  form  of  the  Earth's  shadow,  as  seen  upon  the  Moon 
;n  an  eclipse,  indicates  the  globular  figure  of  the  Earth,  and  the 
consequent  convexity  of  its  surface. 

FOKM   OF  THE   EARTH'S  SHADOW. 


382.  What  further  proof  have  we  that  the  earth  Is  &pherical?    What  rule 
,;poti  this  phenomenon  ?        3S3.  What  other  evidence  that  the  earth  is  a  globe 
What  remarks  respecting  the  curvature  of  the  earth's  surface?    What  rules  laid  down 
fcased  upon  this  curvature? 


THE    PRIMARY    PLANETS- 


'HE    EARTH. 


19f> 


\Vcre  the  Earth  a  cube  as  shown  at  A,  or  in  the  form  of  a.  prism,  as  represented  at  B, 
her  shadow  would  be  more  or  less  cubical  or  prismatic,  as  seen  in  the  cut ;  but  instead 
of  this,  it  is  convex  on  all  sides,  as  represented  at  C,  plainly  indicating  the  convexity  of 
the  Earth  by  which  it  is  caused.  «, 

The  curvature  of  the  Earth  for  one  milt  is  8  inches  ;  and  this  curvature  increases  with 
the  square  of  the  distance.  From  this  general  law  it  will  be  easy  to  calculate  the  distance 
at  which  any  object  whose  height  is  given,  may  be  seen,  or  to  determine  the  height  of  an 
object  when  the  distance  is  known. 

1st.  To  find  the  height  of  the  object  when  the  distance  is  given. 

RULE.  Find  the  square  of  Hie  distance  in  miles,  and  take  two-thirds  of  that  number 


for  the  height  in  feet. 


low  high  must  the  eye  of  an  observer  be  raised,  to  see  the  surface  of  the 
ocean  at  the  distance  of  three  miles?  Ann.  The  square  of  3  ft.  is  9  ft.,  and  %  of  9  ft.  is 
6  ft.  Ex.  2. — Suppose  a  person  can  just  see  the  top  of  a  spire  over  an  extended  plain  of 
ten  miles,  how  high  is  the  steeple  ?  Ans.  The  square  of  10  is  100,  and  %  of  100  is 
66 %  feet. 

2.  To  find  the  distance  when  the  height  is  given. 

RULE.  Increase  the  height  in  feet  one-half,  and  extract  tlie  square  root,  for  the  dis 
tance  in  miles. 

Ex.  1. — How  far  can  a  person  see  the  surface  of  a  plain,  whose  eye  is  elevated  six 
feet  above  it?  Ans.  6,  increased  by  half,  is  9,  and  the  square  root  of  9  is  3 :  the  distance 
is  then  3  miles.  Ex.  2. — To  what  distance  can  a  person  see  a  lighthouse  whose  height 
is  96  feet  from  the  level  of  the  ocean  ?  Ans.  96  increased  by  its  half,  is  144,  and  the 
square  root  of  144,  is  12;  the  distance  is  therefore  12  miles. 

3.  To  find  the  curvature  of  the  Earth  when  it  exceeds  a  mile. 
RULE.  Multiply  the  square  of  the  distance  by  .000126. 

'  384.  Although  it  appears  from  the  preceding  facts,  that  the 
Earth  is  spherical,  yet  it  is  not  a  perfect  sphere.  If  it  were,  the 
length  of  the  degrees  of  latitude,  from  the  equator  to  the  poles, 
would  be  uniformly  the  same  ;  but  it  has  been  found,  by  the 
most  careful  measurement,  that  as  we  go  from  the  equator 
towards  the  poles,  the  length  increases  with  the  latitude. 

These  measurements  have  been  made  by  the  most  eminent  mathematicians  of  different 
countries,  and  in  various  places,  from  the  equator  to  the  arctic  circle.  They  have  found 
that  a  degree  of  latitude  at  the  arctic  circle  was  mint-sixteenths  of  a  mile  longer  than  a 
degree  at  the  equator,  and  that  the  ratio  of  increase  for  the  intermediate  degrees  was 
nearly  as  the  squares  of  the  sines  of  the  latitude.  Thus  the  theory  of  Sir  Isaac  Newton 
was  confirmed,  that  the  body  of  the  Earth  was  more  rounded  and  convex  between  the 
tropics,  but  considerably  flattened  towards  the  poles. 


Places  of 
Observation. 

Latitude. 

Length  of  a  degree  in 
English  miles. 

Observers. 

Pern 

Pennsylvania 
Italy 
France 
England 
Sweden 

Equator. 
39°  12'  N. 
43    01 
46 
51    29   54' 
66    20   10 

68.T32 
6S.896 
68.998 
69.054 
69.146 
69.292 

Bouguer, 
Mason  and  Dixon, 
Boscovich  and  Lemaire, 
Delambre  and  Mechain, 
Mudge, 
Swamberg. 

385.  -These  measurements  prove  the  Earth  to  be  an  oblate 
spheioid,  whose  longest  or  equatorial  diameter  is  7926  miles,  and 
polar  diameter,  7899  miles.  The  mean  diameter  is,  therefore, 
about  7912,  and  their  difference  27  miles.  The  French  Acade- 

884.  But  is  the  earth  a  sphere?  What  proof  to  the  contrary?  885.  What,  then,  is 
»hs  earth's  real  figure  ?  What  difference  in  her  polar  and  equatorial  diameters?  Waut 
demonstration  that  the  earth  is  not  an  exact  sphere  ? 


196  ASTRONOMY. 

my  have  determined  that  the  mean  diameter  of  the  Earth,  from 
the  45th  degree  of  north  latitude,  to  the  opposite  degree  of 
south  latitude,  is  accurately  7912  mifes. 

If  the  Earth  were  an  exact  sphere,  its  diameter  might  bo 
determined  by  its  curvature,  from  a  single  measurement.  Thus, 
in  the  adjoining  figure,  we  have  A  B  equal  to  1  mile,  and  B  D 
equal  to  8  inches,  to  find  A  E,  or  B  E,  which  does  not  sensibly 

/  /       \         differ  from  A  E,  since  B  D  is  only  8  inches.     Now  it  is  a  propo- 

'  *  si^ion  of  Euclid  (B.  3,  prop.  36),  that,  when  from  a  point  with- 
out a  circle,  two  lines  be  drawn,  one  cutting  and  the  other 
touching  it,  the  touching  line  (B  A)  is  a  mean  proportional  be- 
tween the  cutting  line  (B  E)  and  that  part  of  it  (B  D)  without 
the  circle. 

BD:  BA:  :  BEorAE  very  nearly. 
That  is,  1  mile  being  equal  to  63,360  inches, 

8  :  63,360  : :    1  :  7,920.  miles. 
This  is  very  nearly  what  the  most  elaborate  calculations  make  the  Earth's  equatorial 
dia  meter. 

386.  The  Earth,  considered  as  a  planet,  occupies  a  favored 
rank  in  the  Solar  System.  It  pleased  the  All-wise  Creator  to 
assign  its  position  among  the  heavenly  bodies,  where  nearly  all 
the  sister  planets  are  visible  to  the  naked  eye.  It  is  situated 
next  to  Venus,  and  is  the  third  planet  from  the  Sun. 

To  the  scholar  who  for  the  first  time  takes  up  a  book  on  astronomy,  it  will  no  doubt 
seem  strange  to  find  the  Earth  classed  with  the  heavenly  bodies.  For  what  can  appear 
more  unlike,  than  the  Earth,  with  her  vast  and  seemingly  immeasurable  extent,  and  the 
stars,  which  appear  but  as  points?  The  Earth  is  dark  and  opaque,  the  celestial  bodies 
are  brilliant.  We  perceive  in  it  no  motion  ;  while  in  them  we  observe  a  continual  change 
of  place,  as  we  view  them  at  different  hours  of  the  day  or  night,  or  at  different  seasons 
of  the  year. 

387.- It  moves  round  the  Sun  from  west  to  east,  in  365  days, 
5  hours,  48  minutes,  and  48  seconds  ;  and  turns  the  same  way, 
on  its  axis,  in  23  hours,  56  minutes,  and  4  seconds.  The  former 
is  called  its  annual  motion,  and  causes  the  vicissitudes  of  the 
seasons.  The  latter  is  called  its  diurnal  motion,  and  produces 
the  succession  of  day  and  night. 

The  Earth's  mean  distance  from  the  Sun  is  about  95,000,000 
of  miles.  It  consequently  moves  in  its  orbit  at  the  mean  rate  of 
68,000  miles  an  hour.  Its  equatorial  diameter  being  7926  miles, 
it  turns  on  its  axis  at  the  rate  of  1040  miles  an  hour. 

Thus,  tho  Earth  on  which  we  stand,  and  which  has  served  for  ages  as  the  unshaken 
foundation  of  the  firmest  structures,  is  every  moment  turning  swiftly  on  its  center,  aru. 
at  the  same  time,  moving  onwards  with  great  rapidity  through  the  empty  space. 

This  compound  motion  is  to  be  understood  of  the  wftole  Earth,  with  all  that  it  holds 
within  its  substance,  or  sustains  upon  its  surface — of  the  solid  mass  beneath,  of  tho 
ocean  which  flows  around  it,  of  the  air  that  rests  upon  it.  and  of  the  clouds  which  float 
above  it  in  the  air. 

38G.  What  said  of  the  position  of  the  earth  in  the  system  ?  What  remark  as  to  clasaf 
Tying  the  earth  as  a  planet?  387.  State  the  time  of  the  earth's  revolution  around  thn 
Bun?  On  her  own  axis?  What  are  they  called,  respectively ?  What  is  the  earth'e 
distance  from  the  sun?  Its  mean  rate  of  motion  in  its  orbit?  Hourly  motion  of 
at  the  equator?  What  twofold  motion  there?  Includes  what? 


THE  PRIMARY  PLANETS THE  EARTH.        197 

388.  That  the  Earth,  in  common  with  all  the  planets,  revolves 
around  the  Sun  as  a  center,  is  a  fact  which  rests  upon  the  clear- 
est demonstrations  of  philosophy.     That  it  revolves,  like  them, 
upon  its  own  axis,  is  a  truth  which  every  rising  and  setting  sun 
illustrates,  and  which  very  many  phenomena  concur  to  establish. 
Either  the  Earth  moves  around  its  axis  every  day,  or  tfie  whole 
universe  moves  around  it  in  the  same  time.     There  is  no  third 
opinion  that  can  be  formed  on  this  point.     Either  the  Earth 
must  revolve  on  its  axis  every  twenty-four  hours,  to  produce  the 
alternate  succession  of  day  arid  night,  or  the  Sun,  Moon,  planets, 
comets,  fixed  stars,  and  the  whole  frame  of  the  universe  itself, 
must  move,  around  the  Earth,  in  the  same  time. 

389.  To  suppose  the  latter  case  to  be  the  fact,  would  be  to 
cast  a  reflection  on  the  wisdom  of  the  Supreme  Architect,  whose 
laws  are  universal  harmony.     As  well  might  the  beetle,  that  in 
a  moment  turns  on  its  ball,  imagine  the  heavens  and  the  earth 
had  made  a  revolution  in  the  same  instant.     It  is  evident,  that 
in  proportion  to  the  distance  of  the  celestial  bodies  from  the 
Earth,  must,  on  this  supposition,  be  the  rapidity  of  their  move- 
ments.    The  Sun,  then,  would  move  at  the  rate  of  more  than 
400,000  miles  in  a  minute  ;  the  nearest  stars,  at  the  inconceiv- 
able velocity  of  1,400,000,000  of  miles  in  a  second;  and  the 
most  distant  luminaries,  with  a   degree  of  swiftness  which  no 
numbers  could  express,  and  all  this,  to  save  the  little  globe  we 
tread  upon,  from  turning  safely  on  its  axis,  once  in  twenty-four 
hours. 

390.  The  idea  of  the  heavens  revolving  about  the  Earth,  is 
encumbered  with  innumerable  other  difficulties.     We  will  men- 
tion only  one  more.     It  is  estimated  on  good  authority,  that 
there  are  visible,  by  means  of  glasses,  no  less  than  100,000,000 
of  stars,  scattered  at  all  possible  distances  in  the  heavens  above, 
beneath,  and  around  us.     Now,  is  it  in  the  least  degree  probable, 
that  the  velocities  of  all  these  bodies  should  be  so  regulated, 
that,  though  describing  circles  so  very  different  in  dimensions, 
they  should  complete  their  revolutions  in  exactly  the  same  time? 
In  short,  there  is  no  more  reason  to  suppose  that  the  heavens 
revolve  around  the  Earth,  than  there  is  to  suppose  that  they 
revolve  around  each  of  the  other  planets,  separately,  and  at  the 
same  time  ;  since  the  same  apparent  revolution  is  common  to 
them  all,  for  they  all  appear  to  revolve  upon  their  axis,  in  differ- 
ent periods. 

888.  What  two  motions  has  the  eirth?    What  proof  of  her  diurnal  revolution  ?        S3y. 
\\liy  not  suppose  the  heavens  revalve  around  us  ?        3'JO.  What  further  proof? 


198  ASTRONOMY. 

391.  The  rotation  of  the  Earth  determines  the  length  of  the 
day,  and  may  be  regarded  as  one  of  the  most  important  ele- 
ments in  astronomical  science.  It  serves  as  an  universal  measure 
of  time,  and  forms  the  standard  of  comparison  for  the  revolu- 
tions of  the  celestial  bodies,  for  all  ages,  past  and  to  come. 
Theory  and  observation  concur  in  proving,  that  among  the  innu- 
merable vicissitudes  that  prevail  throughout  creation,  the  period 
of  the  Earth's  diurnal  rotation  is  immutable. 


SOLAR  AND  SIDEREAL  TIME. 

392.  The  Earth  performs  one  complete  revolution  on  its  axis 
in  23  hours,  56  minutes,  and  4.09  seconds,  of  solar  time.  This 
is  called  a  sidereal  day,- because,  in  that  time,  the  stars  -appear 
to  complete  one  revolution  around  the  Earth. 

But,  as  the  Earth  advances  almost  a  degree  eastward  in  its 
orbit,  in  the  time  that  it  turns  eastward  around  its  axis,  it  is 
plain  that  just  one  rotation  never  brings  the  same  meridian 
around  from  the  Sun  to  the  Sun  again  ;  so  that  the  Earth 
requires  as  much  more  than  one  complete  revolution  on  its  axis 
to  complete  a  solar  day,  as  it  has  gone  forward  in  that  time. 

SOLAR  AND  SIDEREAL  TIME. 

Q SIDEREAL  DAY 

SOLAR  ^T_— 

L^. " SUN  ON  T3E  ME.RIDIAN 


To  the  man  at  A  the  Sun  (S)  is  exactly  on  the  meridian, 'or  it  is  twelve  o'clock,  noon. 
11i2  Earth  passes  on  from  B  to  D,  and  at  the  same  time  revolves  on  her  axis.  When  she 
reaches  D,  the  man  who  has  stood  on  the  same  meridian  has  made  a  complete  revolution, 
as  determined  by  the  star  G  (which  was  also  on  his  meridian  at  twelve  o'clock  the  day 
before) ;  but  the  Sun  is  now  east  of  the  meridian,  and  he  must  wait/ottr  minutes  for  the 
Earth  to  roll  a  little  further  eastward,  and  bring  the  Sun  again  over  his  north  and  south 
line.  If  the  Earth  was  not  revolving  around  the  Sun,  her  solar  and  sidereal  days  would 
be  the  same ;  but  as»  U  is,  she  has  to  perform  a  little  more  than  one  complete  revolution 
each  solar  day,  to  bring  the  Sun  on  the  meridian. 

393.  It  is  obvious,  therefore,  that  in  every  natural  or  solar 
day,  the  Earth  performs  one  complete  revolution  on  its  axis,  and 
the  365th  part  of  another  revolution.  Consequently,  in  36? 
days,  the  Earth  turns  366  times  around  its  axis.  And  as  every 

391.  What  relaliuu  ha0  the  earth's  diurnal  revolution  to  time  f  What  said  of  its  regu- 
larity? 892.  What  is  tne  time  required  for  a  complete  revolution?  Explain  the differ- 
ence between  solar  and  sidereal  time?  393.  Is  a  solar  day  more  than  a  complete 
revolution  of  the  earth  on  her  axis?  To  what  does  this  excess  amount  in  a  year? 


THE    PRIMARY    PLANETS THE    EARTH.  199 

revolution  of  the  earth  on  its  axis  completes  a  sidereal  day, 
there  must  be  366  sidereal  days  in  a  year.  And,  generally, 
since  the  rotation  of  any  planet  about  its  axis  is  the  length  of  a 
sidereal  day  at  that  planet,  the  number  of  sidereal  days  will 
always  exceed  the  number  of  solar  days  by  one,  let  that  number 
be  what  it  may,  one  revolution  being  always  lost  in  the  course 
of  an  annual  revolution.  This  difference  between  the  sidereal 
and  solar  days  may  be  illustrated  by  referring  to  a  watch  or 
clock.  When  both  hands  set  out  together,  at  12  o'clock  for 
instance,  the  minute  hand  must  travel  more  than  a  whole  circle 
before  it  will  overtake  the  hour  hand,  that  is,  before  they  will 
come  into  conjunction  again. 

394.  In  the  same  manner,  if  a  man  travel  around  the  Earth 
eastwardly,  no  matter  in  what  time,  he  will  reckon  one  day  more, 
on  his  arrival  at  the  place  whence  he  set  out,  than  they  do  who 
remain  at  rest ;  while  the  man  who  travels  around  the  Earth 
westwardly  will  have  one  day  less.     From  which  it  is  manifest, 
that  if  two  persons  start  from  the  same  place  at  the  same  time> 
but  go  in  contrary  directions,  the  one  traveling  eastward  and 
the  other  westward,  and  each  goes  completely  around  the  globe, 
although  they  should  both  arrive  again  at  the  very  same  hour 
at  the  same  place  from  which  they  set  out,  yet  they  will  disagree 
two  whole  days  in  their  reckoning.     Should  the  day  of  their 
return,  to  the  man  who  traveled  westwardly,   be  Monday,  to 
the  man  who  travelled  eastwardly,  it  would  be  Wednesday  ; 
while  to  those  who  remained  at  the  place  itself,  it  would  be 
Tuesday. 

395.  Nor  is  it  necessary,  in  order  to  produce  the  gain  or  loss 
of  a  day,  that  the  journey  be  performed  either  on  the  equator, 
or  on  any  parallel  of  latitude  :  it  is  sufficient  for  the  purpose, 
that  all  the  meridians  of  the  Earth  be  passed  through,  eastward 
'or  westward.     The  time,  also,  occupied  in  the  journey,  is  equally 
unimportant ;  the  gain  or  loss  of  a  day  being  the  same,  whether 
the  Earth  be  traveled  around  in  24  years,  or  in  as  many  hours. 

396.  It  is  also  evident,  that  if  the  Earth  turned  around  its 
axis  but  once  in  a  year,  and  if  the  revolution  was  performed  the 
same  way  as  its  revolution  around  the  Sun,  there  would  be  per- 
petual day  on  one  side  of  it,  and  perpetual  night  on  the  other. 

Flence  what  general  rule  ?  What  illustration  referred  to?  894.  What  effect  has  tra- 
veling east  or  west,  upon  time  ?  Hence  what  result?  395.  Is  it  important  that  the  sup- 
posed journeys  be  performed  in  a  short  period?  896.  How  would  it  be  if  tl.e  Eartl. 
revolved  oc  >ier  axis  but  once  a  year? 


200  ASTRONOMY. 

Prom  these  facts  the  pupil  will  readily  comprehend  the  principles  involved  in  a  curious 
problem  which  appeared  a  few  years  ago.  It  was  gravely  reported  by  an  American  ship, 
that,  in  sailing  over  the  ocean,  it  chanced  to  find  six  Sundays  in  February.  The  /act 
was  insisted  on,  and  a  solution  demanded.  There  is  nothing  absurd  in  this.  The  man 
who  truvels  around  the  earth  eastwardly,  will  see  the  Sun  go  down  a  little  earlier  every 
succeeding  day,  than  if  he  had  remained  at  rest;  or  earlier  than  they  do  who  live  at  the 
place  from  which  he  set  out.  The  faster  he  travels  towards  the  rising  sun,  the  sooner 
will  it  appear  above  the  horizon  in  the  morning,  and  so  much  sooner  will  it  set  in  the 
evening.  What  he  thus  gains  in  time,  will  bear  the  same  proportion  to  a  solar  day,  as 
the  distance  traveled  does  to  the  circumference  of  the  Earth.  As  the  globe  is  360  degrees 
in  circumference,  the  Sun  will  appear  to  move  over  one  twenty-fourth  part  of  its  surface, 
or  14°  every  hour,  which  is  4  minutes  to  one  degree.  Consequently,  the  Sun  will  rise, 
come  to  the  meridian,  and  set,  4  minutes  sooner,  at  a  place  1"  east  of  us,  than  it  will 
with  us ;  at  the  distance  of  2°  the  Sun  will  rise  and  set  8  minutes  sooner ;  at  the  distance 
of  3°,  12  minutes  sooner,  and  so  on. 

Now  the  man  who  travels  one  degree  to  the  east,  the  first  day  will  have  the  Sun  on  his 
meridian  4  minutes  sooner  than  we  do.  who  are  at  rest ;  and  the  second  day  8  minutes 
sooner,  and  on  the  third  day  1U  minutes  sooner,  and  so  on  ;  each  successive  day  being 
completed  4  minutes  earlier  than  the  preceding,  until  he  arrives  again  at  the  place  from 
which  he  started  :  when  this  continual  gain  of  4  minutes  a  day  will  have  amounted  to  a 
whole  day  in  advance  of  our  time :  he  having  seen  the  Sun  rise  and  set  once  more  than 
we  have.  Consequently,  the  day  on  which  he  arrives  at  home,  whatever  day  of  the 
week  it  may  be,  is  one  day  in  advance  of  ours,  and  he  must  needs  live  that  day  over 
again,  by  calling  the  next  day  by  the  same  name,  in  order  to  make  the  accounts 
harmonize. 

If  this  should  be  the  last  day  of  February  in  a  bissextile  year,  it  would  also  be  the 
name  day  of  the  week  that  the  first  was,  and  be  six  times  repeated,  and  if  it  should 
happen  on  Sunday,  he  would,  under  these  circumstances,  have  six  Sundays  in  February. 

Again  :  whereas  the  man  who  travels  at  the  rate  of  one  degree  to  the  east,  will  have 
al!  his  days  4  minutes  shorter  than  ours,  so,  on  the  contrary,  the  man  who  travels  at  the 
same  rate  towards  the  west,  will  have  all  his  days  4  minutes  longer  than  ours.  When  he 
has  finished  the  circuit  of  the  Earth,  and  arrived  at  the  place  from  which  he  first  set 
out,  he  will  have  seen  the  Sun  rise  and  set  once  less  than  we  have.  Consequently,  the 
day  he  gets  home  will  be  one  day  after  the  time  at  that  place;  for  which  reason,  if  he 
arrives  at  home  on  Saturday,  according  to  his  own  account,  he  -will  have  to  call  the  next 
day  Monday  ;  Sunday  having  gone  by  before  he  reached  home.  Thus,  on  whatever  day 
of  the  week  January  should  end,  in  common  years,  he  would  find  the  same  day  r^p^ated 
only  three  times  in  February.  If  January  ended  on  Sunday,  he  would,  under  these  cir- 
eumstances,  find  only  tliree  Sundays  in  February. 

397.  The  Earth's  motion  about  its  axis  being  perfectly  equable 
and  uniform  in  every  part  of  its  annual  revolution,  the  sidereal 
days  are  always  of  the  same  length,  but  the  solar  or  natural  days 
vary  very  considerably  at  different  times  of  the  year.  This  varia- 
tion is  owing  to  two  distinct  causes,  the  inclination  of  the  Earth's 
axis  to  its  orbit,  and  the  inequality  of  its  motion  around  the  Sun. 
From  these  two  causes  it  is,  that  the  time  shown  by  a  well-regu: 
lated  clock  and  that  of  a  true  sun-dial  are  scarcely  ever  the 
same.  The  difference  between  them,  which  sometimes  amounts 
to  16^  minutes,  is  called  the  Equation  of  Time,  or  the  equation 
of  solar  days. 

What  curious  facts  accounted  for  T  What  supposition  of  a  man  traveling  eastward 
one  degree  a  day?  What  effect  upon  the  time  of  the  Sun's  passing  the  meridian?  Upon 
the  length  of  his  daj  ?  What  change  of  name  may  it  require  ?  897.  Are  the  solar 
and  sidereal  days  alik s  uniform  as  to  length  ?  Why  do  solar  days  vary  in  length?  WUj 
do  not  a  dial  and  clock  agree  ?  What  is  the  Equation  of  Time  ? 


THE  PRIMARY  PLANETS THE  EARTH 


201 


EQUATION  OP  TIMB 

The    difference    between  N 

nean  and  apparent  time, 
or,  in  other  words,  between 
Equinoctial  and  Ecliptic 
time,  may  be  further  shown 
by  this  figure,  which  repre- 
sents the  circles  of  the 
sphere  Let  it  be  first  pre- 
mised, that  equinoctial  time 
is  clock  time ;  and  that 
ecliptic  time  is  solar  or 
apparent  time.  It  appears 
that  from  Aries  to  Cancer, 
the  Sun  in  the  ecliptic  comes 
to  the  meridian  before  the 
equinoctial  Sun ;  from  Can- 
cer to  Libra,  after  it ;  from 
Libra  to  Capricorn  before 
it ;  and  from  Capricorn  to 
Aries  after  it.  If  we  notice 
what  months  the  Sun  is  in 
these  several  quarters,  we 
shall  find  that  from  the  25th 
of  December  to  the  16th  of 
April,  and  from  the  16th  of 
June  to  the  1st  of  Septem- 
ber, the  clock  i»  faster  than 
the  sun-dial ;  and  that,  from 

the  16th  of  April  to  the  16th  of  June,  and  from  the  1st  of  September  to  the  25th  of  De- 
the  sun-dial  is  faster  than  the  clock. 

398.  It  is  an  universal  fact,  that,  while  none  of  the  planets  are 
perfect  spheres,  none  of  their  orbits  are  perfect  circles.     The 
planets  all  revolve  about  the  Sun,  in  ellipses  of  different  degrees 
of  eccentricity  ;  having  the  Sun,  not  in  the  center  of  the  ellipse, 
but  in  one  of  its  foci. 

The  figure  A  D  B  E  is  an  ellipse.  The  line  A  B  is 
called  the  transverse  axis,  and  the  line  drawn  through 
the  middle  of  this  line,  and  perpendicular  to  it,  is  the 
conjugate  axis.  The  point  C,  the  middle  of  the  trans- 
verse axis,  is  the  center  of  the  ellipse.  The  points 
P  and  f,  equally  distant  from  C,  are  called  the  foci. 
C  F,  the  distance  from  the  center  to  one  of  the  foci, 
is  called  the  eccentricity.  The  orbits  of  the  planets 
being  ellipses,  having  the  Sun  in  one  of  the  foci,  if 
A  D  B  E  be  the  orbit  of  a  planet,  with  the  Sun  in  the 
focus  F,  when  the  planet  is  at  the  point  A,  it  will  be  in 
its  perihelion,  or  nearest  the  Sun  ;  and  when  at  the 
point  B  in  ita  aphelion,  or  at  its  greatest  distance 
from  the  Sun.  The  difference  in  these  distances  is 
evidently  equal  to  P  f,  that  is,  equal  to  twice  the  eccentricity  of  its  orbit.  In  every  revo- 
lution, a  planet  passes  through  its  perihelion  and  aphelion.  The  eccentricity  jf  the 
Earth's  orbit  is  about  one  and  a  half  millions  of  miles ;  hence  she  is  3,000,000  of  miles 
nearer  the  Sun  in  her  perihelion,  than  in  her  aphelion. 

Now  as  the  Sun  remains  fixed  in  the  lower  focus  of  the  Earth's  orbit,  it  is  easy  to  per- 
ceive that  a  line,  passing  centrally  through  the  Sun  at  right  angles  with  the  longer  axis 
of  the  orbit,  will  divide  it  into  two  unequal  segments.  Precisely  thus  it  is  divided  by 
the  equinoctial. 

399.  That  portion  of  the  Earth's  orbit  which  lies  above  the 


898.  What  is  the  true  form  of  the  planets'  orbits  ?     Why  ic  equinoctial  time  irregular? 
899.  How  is  the  Earth'*  orbit  divided  by  the  equinoctial  ? 


'202  ASTRONOMY. 

Sun,  or  north  of  the  equinoctial,  contains  about  184  degrees  ; 
while  that  portion  of  it  which  lies  below  the  Sun,  or  south  of  the 
equinoctial,  contains  only  176  degrees.  This  fact  shows  why 
the  Sun  continues  about  eight  days  longer  on  the  north  side  of 
the  equator  in  summer,  than  it  does  on  the  south  side  in  winter. 
The  exact  calculation,  for  the  year  1830,  is  as  folio »vs  : 

d.  h.  ra.      d.      h.     m. 

From  the  vernal  equinox  to  the  summer  solstice,                 =92  21  19  I    -too    -11     -in 

From  the  summer  solstice  to  the  autumnal  equinox,             =  93  14  1  | 

From  the  autumnal  equinox  to  the  winter  solstice,               =  89  17  17  \    17Q    1S    <,rt 

From  the  winter  solstice  to  the  vernal  equinox,                    =89  1  13  J 

Difference  in  favor  of  the  north  side,  =     7    16    49 

The  points  of  the  Earth^s  orbit  which  correspond  to  its  greatest  and  least  distances 

from  the  Sun,  are  called,  the  former  the  Apogee,  and  the  latter  the  Perigee;  two  Greek 

words,  the  former  of  which  signifies  from  the  EariJi,  and  the  latter  about  the  Earth. 

These  points  are  also  designated  by  the  common  name  of  Apsides. 

400.  The  Earth  being  in  its  perihelion  about  the  1st  of  Jan- 
uary, and  in  its  aphelion  the  1st  of  July;  we  are  3,000,000  of 
miles  nearer  the  Sun  in  winter  than  in  midsummer.     The  reason 
why  we  have  not,  as  might  be  expected,  the  hottest  weather 
when  the  Earth  is  nearest  the  Sun,  is,  because  the  Sun,  at  that 
time,  having  retreated  to  the  southern  tropic,  shines  so  obliquely 
on  the  northern  hemisphere,  that  its  rays  have  scarcely  half  the 
effect  of  the  summer  Sun  ;  and  continuing  but  a  short  time  above 
the  horizon,  less  heat  is  accumulated  by  day  than  is  dissipated 
by  night. 

401.  As  the  Earth  performs  its  annual  revolution  around  the 
Sun,  the  position  of  its  axis  remains  invariably  the  same  ;  always 
pointing  to  the  North  Pole  of  the  heavens,  and  always  main- 
taining the  same  inclination  to  its  orbit.     This  seems  to  be  pro- 
videntially ordered  for  the  benefit  of  mankind.     If  the  axis  of 
the  Earth  always  pointed  to  the  center  of  its  orbit,  all  external 
objects  would  appear  to  whirl  about  our  heads  in  an  inexplicable 
maze.     Nothing  would  appear  permanent.     The  mariner  could 
no  longer  direct  his  course  by  the  stars,  and  every  index  in 
nature  would  mislead  us. 

What  phenomenon  does  this  explain  ?  400.  When  is  the  Earth  in  Its  perihelion  ?  It 
aphelion  ?  What  difference  in  its  distance  from  the  Sun  ?  Why,  then,  have  we  not  tho 
Traraest  weather  in  January  ?  401.  What  said  of  the  permanency  of  the  Earth's  axis? 
How  H-ould  it  be  if  either  pole  was  toward  the  Sun* 


THE    MOON HER    DISTANCE,    MOTIONS,    PHASES.         203 

CHAPTER   IV. 

THE  MOON— HE±v  DISTANCE,  MOTIONS,  PHASES,  &o. 

402.  THERE  is  no  object  within  the  scope  of  astronomical 
observation  which  affords  greater  variety  of  interesting  investi- 
gation than  the  various  phases  and  motions  of  the  Moon.  From 
them  the  astronomer  ascertains  the  form  of  the  Earth,  the  vicis- 
situdes of  the  tides,  the  causes  of  eclipses  and  occupations,  the 
distance  of  the  Sun,  and,  consequently,  the  magnitude  of  the 
solar  system.  These  phenomena,  which  are  perfectly  obvious  to 
the  unassisted  eye,  served  as  a  standard  of  measurement  to  all 
nations,  until  the  advancement  of  science  taught  them  the  advan- 
tages of  solar  time.  It  is  to  these  phenomena  that  the  naviga- 
tor is  indebted  for  that  precision  of  knowledge  which  guides  him 
with  well-grounded  confidence  through  the  pathless  ocean. 

The  Hebrews,  the  Greeks,  the  Romans,  and,  in  general,  all 
the  ancients,  used  to  assemble  at  the  time  of  new  or  full  Moon, 
to  discharge  the  duties  of  piety  and  gratitude  for  Irer  unwearied 
attendance  on  the  Earth,  and  all  her  manifold  uses. 

The  philosophy  of  the  changes  of  the  Moon  is  illustrated  by 
the  following  cut : 

PHILOSOPHY  OF  THE   MOON'S  CHANGES. 


X"*         FIRST  pR. 

>s 

<er.  €>••••" 

•         ^"  V^          C$ 

>  €) 

r>^J/      \                           rxs"^^^--^"""*"  

/     /          II 

\     OM*-?"..^  

?        FOT.L 

Ney—  --,  

sC-O~~f|- 

—  "ic"i^  f\.-\        

-     A.^-^--1-. 

\  \  '  11 

H    /      j 

GIBBOOSJQ               QJ 

e.  ^e- 

-*c 

x-c..^ 

s 

This  cut  represents  the  moon  revolving  eastward  around  the  Earth.  In  the  t/utsido 
circle,  she  is  represented  as  she  would  appear,  if  viewed  from  a  direction  at  right  anglea 
with  the  plane  of  her  orbit.  The  side  toward  the  Sun  is  enlightened  in  every  case,  and 
she  appears  like  a  half  moon  at  every  point. 

402.  What  sail  of  the  Moon's  motions  and  phases?  What  learned  from  them?  How 
used  anciently?  How  at  the  present  time?  How  did  the  ancients  observe  the  new  au! 
full  moons? 

9* 


204  ASTRONOMY. 

The  interior  suit  represents  her  as  she  appears  when  viewed  from  the  earth.  At  A  It  io 
New  Moon  ;  and  if  seen  at  all  so  near  the  Sun,  she  would  appear  like  a  dark  globe.  At 
B  she  would  appear  like  a  crescent,  concave  toward  the  east.  At  C,  more  of  her  enlight- 
ened side  is  visible  ;  at  D  still  more  ;  and  at  E  the  enlightened  hemisphere  is  fully  in 
view.  We  then  call  her  a  Full  Moon.  From  E  around  to  A  again,  the  dark  portion 
becomes  more  and  more  visible,  as  the  luminous  part  goes  out  of  view,  till  she  comes  to 
her  change  at  A.  When  at  D  and  F  the  moon  is  said  to  be  gibbous. 

403.  When  the  Moon,  after  having  been  in  conjunction  with 
the  Sun,  emerges  from  his  rays,  she  first  appears  in  the  evening, 
a  little  after  sunset,  like  a  fine  luminous  crescent,  with  its  convex 
side  towards  the  Sun.     If  we  observe  her  the  next  evening,  we 
find  her  about  13°  farther  east  of  the  Sun  than  on  the  preceding 
evening,  and  her  crescent  of  light  sensibly  augmented.     Repeat- 
ing these  observations,  we  perceive  that  she  departs  farther  and 
farther  from  the  Sun,  as  her  enlightened  surface  comes  more  and 
more  into  view,  until  she  arrives  at  her  first  quarter,  and  comes 
to  the  meridian  at  sunset.     She  has  then  finished  half  her  course 
from  the  new  to  the  full,  and  half  her  enlightened  hemisphere  is 
turned  towards  the  Earth. 

404.  After  her  first  quarter,  she  appears  more  and  more  gib- 
bous, as  she  recedes  farther  and  farther  from  the  Sun,  until  she 
has  completed  just  half  her  revolution  around  the  Earth,  and  is 
seen  rising  in  the  east  when  the  Sun  is  setting  in  the  west.    She 
then  presents  her  enlightened  orb  full  to  our  view,  and  is  said 
to  be  in  opposition;  because  she  is  then  on  the  opposite  side  of 
the  Earth  with  respect  to  the  Sun, 

la  the  first  half  of  her  orbit  she  appears  to  pass  over  our 
heads  through  the  upper  hemisphere  ;  she  now  descends  below 
the  eastern  horizon  to  pass  through  that  part  of  her  orbit  which 
lies  in  the  lower  hemisphere. 

405.  After  her  full  she  wanes  through  the  same  changes  of 
pearance  as  before,  but  in  an  inverted  order  ;  and  we  see  her  in 
the  morning  like  a  fine  thread  of  light,  a  little  west  of  the  rising 
Sun.     For  the  next  two  or  three  days  she  is  lost  to  our  view, 
rising  and  setting  in  conjunction  with  the  Sun  ;  after  which,  she 
passes  over,  by  reason  of  her  daily  motion,  to  the  east  side  of 
the  Sun,  and  we  behold  her  again,  a  new  Moon,  as  before.     In 
changing  sides  with  the  Sun,  she  changes  also  the  direction  of 
her  crescent.     Before  her  conjunction  it  was  turned  to  the  east ; 
it  is  now  turned  towards  the  west.     These  different  appearances 
of  the  Moon  are  called  her  phases.     They  prove  that  she  shines 

403.  Explain  the  cause  of  the  changes  of  the  Moon  ?  404.  Row  after  her  first  quarter? 
406.  How  after  her  full?  What  change  in  her  crescent?  What  do  the  Moon's  phasea 
prove  ? 


THE    .ICON  -  HER    MOTIONS,    PHASES,    ETC.  20i> 

fK»t  by  any  light  of  her  own  ;  if  she  did,  being  globular,  wo 
should  always  see  her  a  round  full  orb  like  the  Sun. 

406.  The  Moon  is  a  satellite  to  the  Earth,  about  which  she 
revolves  in  an  elliptical  orbit,  in  29  days,  12  hours,  44  minutes, 
and  3  seconds  ;  the  time  which  elapses  between  one  new  moon 
and  another.  This  is  called  her  synodic  revolution.  Her  revo- 
lution from  any  fixed  star  to  the  same  star  again,  is  called  her 
periodic  or  sidereal  revolution.  It  is  accomplished  in  27  days,  7 
hours,  43  minutes,  and  11£  seconds  ;  but  in  this  time,  the  Earth 
has  advanced  nearly  as  many  degrees  in  her  orbit  ;  consequently, 
the  Moon,  at  the  end  of  oce  complete  revolution,  must  go  as 
many  degrees  farther,  before  she  will  come  again  into  *he  same 
position  with  respect  to  the  Sun  and  the  Earth. 


SIDEREAL  AMD  SYNODIC  REVOLUTIONS  OP  THK  MOON. 


•\ 


SUN  AND   MOON   IN  CONJUNCT  ION- NEW  MOON/ 

A- 


On  the  right,  the  earth  is  shown  in  her  orbit,  revolving  around  the  sun,  and  the  moon 
In  her  orbit,  revolving  around  the  earth.  At  A,  the  sun  and  uioon  are  in  conjunction, 
or  it  is  New  Moon.  As  the  earth  passes  from  D  to  E,  the  moon  passes  around  from  A  to 
B,  or  the  exact  point  in  her  orbit  where  she  was  27^  days  before.  But  she  is  still  west 
of  the  sun,  and  must  pass  on  from  B  to  C,  or  1  day  and  20  hours  longer,  before  she  can 
again  come  in  conjunction  with  him.  This  1  day  and  20  hours  constitutes  the  difference 
between  a  sidereal  and  a  synodic  revolution. 

The  student  will  perceive  that  the  difference  between  a  sidereal  and  synodic  revolution 
of  the  moon,  like  that  between  solar  and  sidereal  time,  is  due  to  the  same  cause,  namely, 
the  revolution  of  the  earth  around  the  sun. 

407.  Lying  along  the  Moon's  path,  there  are  nine  conspicu- 
ous stars  that  are  used  by  nautical  men  for  determining  their 
longitude  at  sea,  thence  called  nautical  *tars.  These  stars  are, 
Arietes,  Aldebaran,  Pollux,  Regulus,  Spica  Virginis,  Antares, 
Altaire,  Fomalhaut,  and  Markab. 

The  true  places  of  these  stars,  for  every  day  in  the  year,  are  given  in  the  Nautical 
Vlmanac,  a  valuable  work  published  annually  by  the  English  "  Board  of  Admiralty,"  to 
^uide  mariners  in  navigating  the  seas.  They  are  usually  published  two  or  three  years  in 
vdvance.  for  the  benefit  of  long  voyages 

Let  A  in  the  cut  represent  Greenwich  Observatory,  near  London.  B  is  the  Moon,  and 
C  her  apparent  place  among  the  distant  stars,  about  40*  west  of  the  star  D.  The  ship-B, 
Laving  Greenwich  time,  as  well  as  her  own  local  time,  sails  from  London  westward  ; 

406.  Form  of  the  lunar  orbit?  Time  of  synodic  revolution?  Of  sidereal  revolution? 
Wl-at  difierence  ?  407.  What  are  the  nautical  stars?  Can  you  explain  how  longitude 
i  ascertained  by  them? 


^06 


ASTRONOMY. 


but  on  observing  the  Moon  when,  by  Greenwich 
time,  she  ought  to  be  at  C,  she  is  found  to  be  at  F,  or 
only  about  20°  west  of  the  star  D.  It  is,  therefore, 
obvious  that  the  ship  is  west  of  Greenwich,  as  the 
Moon  appears  east  of  her  Greenwich  place.  Prom 
this  difference  between  her  place  as  laid  down  in  the 
tables,  and  her  observed  place,  as  referred  to  cer- 
tain prominent  stars,  the  mariner  determines  ho;v 
far  he  is  east  or  west  of  the  meridian  of  Greenwich. 
The  Moon's  geocentric  place  (or  place  as  viewed 
from  the  center  of  the  Earth)  may  be  given  instead 
of  her  Greenwich  place,  and  the  same  conclusions 
arrived  at.  In  either  case,  this  is  called  the  liwar 
method  of  determining  the  longitude.  It  is  also  ascer- 
tained by  simple  comparison  of  local  and  standard 
time,  that  a  man,  says  Sir  John  Herschel,  by  merely 
measuring  the  Moon's  apparent  distance  from  a  star, 
with  a  little  portable  instrument  held  in  his  hand, 
and  applied  to  his  eye,  even  with  so  unstable  a  foot- 
ing as  the  deck  of  a  ship,  shall  say  positively  wilhin 
five  miles  where  he  is,  on  a  boundless  ocean,  cannot 
but  appear  to  persons  ignorant  of  physical  astronomy 
an  approach  to  the  miraculous.  And  yet,  says  he 
the  alternatives  of  life  and  death,  wealth  and  ruin 
are  daily  and  hourly  staked,  with  perfect  confidence 
on  these  marvellous  computations. 

408.  The  Moon  is  the  nearest  of  all  the  heavenly  bodies,  being 
about  thirty  times  the  diameter  of  the  Earth,  or  239,000  miles, 
distant  from  us.  Her  mean  daily  motion  in  her  orbit  is  nearly 
fourteen  times  as  great  as  the  Earth's  ;  since  she  not  only  accom- 
panies the  Earth  around  the  Sun  every  year,  but,  in  the  mean 
time,  performs  nearly  thirteen  revolutions  about  the  Earth. 

Although  the  apparent  motion  of  the  Moon  in  her  orbit  is  greater  than  that  of  any 
other  heavenly  body,  since  she  passes  over,  at  a  mean  rate,  no  less  than  18°  10'  35"  in  a 
day ;  yet  this  is  to  be  understood  as  angular  motion, — motion  in  a  small  orbit — and 
therefore  embracing  a  great  number  of  degrees,  and  but  comparatively  few  miles. 


409.  The  point  in  the  Moon's  orbit 
nearest  the  Earth  is  called  Perigee,  from 
the  Greek  peri,  about,  and  ge,  the  earth. 
The  point  most  distant  is  called  Apogee, 
from  apo,  from,  and  ge,  the  earth.    These 
two  points  are  also  called  the  apsides 
of  her  orbit ;  and  a  line  joining  then^ 
the  line  of  the  apsides. 

See  the  Moon  in  apogee  and  perigee  in  the  cut.    Tbo 
singular  of  apsides  is  apsis. 

410.  The  line  of  the  apsides  of  the 
Moon's  orbit  is  not  fixed  in  the  ecliptic, 
but  revolves  slowly  around  the  ecliptic, 


408.  The  Moon's  distance?  Daily  motion  in  orbit?  How  many  degrees?  409 
Perigee  and  Apogee  ?  Derivation  ?  What  other  name  for  these  two  points  ?  What,  it 
the  line  of  the  apsides ?  410.  Is  this  line  stationary?  What  motion?  Its  period  cf 
roTolut'on  ? 


THE  MOON HER   MOTIONS,  PHASES,  ETC.     207 

from  west  to  east,  in  the  period  MOTION  ov  TnB  AP8n)E8- 

of  about  nine  years. 

In  the  adjoining  cut,  an  attempt  is  made  to 
represent  this  motion.  At  A,  the  line  of  the 
apsides  points  directly  to  the  right  and  left ; 
but  at  B,  C,  and  D,  it  is  seen  changing  its 
direction,  till  at  E  the  change  is  very  percep- 
tible when  compared  with  A.  But  the  same 
ratio  of  change  continues ;  and  at  the  end  of 
a  year,  when  the  Earth  reaches  A  again,  the 
line  of  the  apsides  is  found  to  have  revolved 
eastward  to  the  dotted  line  I  K,  or  about  40°. 
In  nine  years  the  aphelion  point  near  A  will 
have  made  a  complete  revolution,  and  return- 
ed to  its  original  position. 

411.  The  line  of  the  Moon's 
nodes  is  also  in  revolution  ;  but 

it  retrogrades  or  falls  back  westward,  making  the  circuit  of  the 
ecliptic  once  in  about  nineteen  years. 

4 1 2.  Though  her  orbit  is  an  ellipse,  B  ^.  m0'.-- •*-. 
with  respect  to  the  Earth,  it  is,  in          ....;'-•©"•* 
reality,   an  irregular  curve,   always       .*<« 

concave  toward  the.  Sun,  and  crossing      .J£ 
the  Earth's  orbit  every  13°  nearly.      f  || 

If  the  Earth  stood  still  in  her  orbit,  the  Moon      Xj.., 
would  describe  just  such  a  path  in  the  ecliptic  as      f\ 
she  describes  with  respect  to  the  Earth.  ^  ^ 

If  the  Earth  moved  but  slowly  on  her  way,  the 
Moon  would  actually  retrograde  on  the  ecliptic  at 
tho  time  of  her  change,  and  would  cross  her  own       ,     * 
path  at  every  revolution,  as  shown  in  the  adjoin-  ^ 

ing  figure.      But  as    the  Earth    advances    some 

46,000,000  of  miles,  or  near  100  times  the  diameter  ''•-*''    *»•—•• 

of  the  Moon's  orbit,  during  a  single  lunation,  it  is 

evident  that  the  Moon's  orbit  never  can  return  into  itself,  or  retrograde,  as  here  repre- 
sented. 

That  the  lunar  orbit  is  always  concave  toward  the  Sun,  may  be  demonstrated  by  the 
above  diagram. 

THE  MOON'S  ORBIT  ALWAYS  CONCAVE  TOWARD  THB  SUN. 


"      "" 
° 


Let  the  upper  curve  line  A  B  represent  an  arc  of  the  Earth's  orbit,  equal  tc  that 
passed  through  by  the  Earth  during  half  a  lunation.  Now  the  radius  and  arc  being 
known,  it  is  found  that  the  chord  A  B  must  pass  more  than  400,000  miles  within  tho 
Earth.  But  as  the  Moon  departs  only  240,000  from  the  Earth,  as  shown  in  the  figure,  it 
follows  that  she  must  describe  the  curve  denoted  by  the  middle  line,  which  is  concave 
toward  the  Sun. 

This  subject  may  be  still  further  illustrated  by  the  following  cut : 


411.  How  with  the  line  of  the  Moon's  nodes?        412.  What  is  the  actual  form  of  tho 
Moon's  orbit?     How  if  the  Earth  stood  still ?     Row  if  she  moved  but  slowly?     How  is 
,c  Moon's  orbit  demonstrated  to  be  always  concave  towards  the  Sun  ? 


208 


ASTRONOMY. 


TH*  MOON'S    PATH  DURING  A  COMPLETE  LCNATIOW. 
C  B 


Bere  the  plain  line  represents  the  Earth's  orbit,  and  the  dotted  one  that  of  the  Moon.  Ai 
A.  ihe  Moon  crosses  the  Earth's  track  240,000  miles  behind  her.  She  gains  on  the  Earth, 
till  in  seven  days  she  passes  her  at  B  as  a  Full  Moon.  Continuing  to  gain  on  the  Earth, 
Bhe  crosses  her  orbit  at  C,  240,000  miles  ahead  of  her,  being  then  at  her  Third  Qiuiner. 
From  this  point  the  Earth  gains  upon  the  Moon,  till  seven  days  afterward  she  overtakes 
her  at  D  as  a  New  Moon.  From  D  to  E  the  Earth  continues  to  gain,  till  at  E  the  Moon 
crosses  240,000  behind  the  Earth,  as  she  had  done  four  weeks  before  at  A.  Thus  the 
Moon  winds  her  way  along,  first  within  and  then  without  the  Earth  ;  always  gaining  upon 
us  when  outside  of  our  orbit,  and  falling  behind  us  when  within  it. 

The  small  circles  in  the  cut  represent  the  Moon's  orbit  with  respect  to  the  Earth,  which 
is  as  regular  to  us  as  if  the  Earth  had  no  revolution  around  the  Sun. 

413.  The  moon  never  retrogrades  on  the  ecliptic,  or  returns 
into  her  own  path  again  ;'  but  is  always  advancing  with  the 
Earth,  at  the  rate  of  not  less  than  65,700  miles  per  hour. 

KOON'S  PATH.  The  Moon's  orbitual  velocity,  with  respect  to  the 

Earth,  is  about  2300  miles  p«r  hour.  When  outside 
the  Earth,  as  at  B,  in  the  last  figure,  she  gain*  28- *> 
miles  per  hour,  which  added  to  the  Earth's  velocitj 
would  give  70,300  miles  as  the  hourly  velocity  of  the 
Moon.  When  within  the  Earth's  orbit,  as  at  D,  she 
loses  2300  miles  per  hour,  which,  abstracted  from 
68,000  miles  (the  Earth's  hourly  velocity),  would  leave 
65,700  miles  as  the  slowest  motion  of  the  Moon  iu 
space,  even  when  she  is  falling  behind  the  Earth. 

Could  we  look  down  perpendicularly  upon  the  eclip- 
tic, and  see  the  paths  of  the  Earth  and  Moon,  we  should 
see  the  latter  pursuing  her  serpentine  course,  first 
within  and  then  outside  our  globe,  somewhat  as  repre- 
sented by  the  dotted  line  in  the  annexed  figure.  Her 
path,  however,  would  be  concave  toward  the  Sun,  as. 
shown  on  the  preceding  page,  and  not  convex,  as  we 
were  obliged  to  represent  it  here  in  so  small  a  diagram. 

414.  In  her  journey  ings  eastward,  the  Moon  often  seems  tc 

run  over  and  obscure  the  distant  planets 
and  stars.  This  phenomenon  is  called 
an  occultation. 

The  adjoining  cut  represents  the  new  Moon  as  ju?< 
about  to  obscure  a  distant  star,  by  passing  between 
us  and  it.  In  1850,  she  occulted  Jupiter  for  three 
revolutions  in  succession — viz.,  Jan.  30th,  Feb.  27th, 
and  March  26th.  Through  a  telescope,  the  Moon  \? 
seen  to  be  constantly  obscuring  stars  that  are  invisi 
ble  to  the  naked  eye.  They  disappear  behind  the 
Moon's  eastern  limb,  and  in  a  short  time  reappear 
from  behind  her  western ;  thus  distinctlj  exhibiting 
her  eastward  motion. 


413.  Does  she  ever  retrog-ade  on   the  ecliptic?    What  13  her  slowest  motion?    How 
•Jemonstrated  ?        414.  Whui  is  an  occultation  f    Remarks  respecting  this  phenomenon  7 


THE  MOOI*  —HER  MOTIONS,  PHASES,  ETC. 


209 


MOON'S  REVOLUTION. 


415.  The  Moon  revolves  once  on  her  axis  exactly  in  the  time 
that  she  performs  her  revolution  around  the  Earth.     This  is  evi- 
dent from  Ler  always  presenting  the  same  side  to  the  Earth  ; 
for  if  she  had  no  rotation  upon  an  axis,  every  part  of  her  surface 
would  be  presented  to  a  spectator  on  the  Earth,  in  the  course 
of  her  synodical  revolution.     It  fol- 
lows, then,  that  there  is  but  one  day 

and  night  in  her  year,  containing, 
both  together,  29  days,  12  hours, 
44  minutes,  and  3  seconds. 

Suppose  a  monument  erected  upon  the  Moon's 
surface,  so  as  to  point  toward  the  Earth  at  New 
Afoon,  as  represented  at  A.  From  the  Earth  it 
would  appear  in  the  Moon's  center.  Now  if  the 
Moon  so  revolve  upon  her  axis,  in  the  direction  of 
the  arrows,  as  tu  keep  the  pillar  pointing  directly 
toward  the  Earth,  as  shown  at  A,  B,  C,  and  D,  and 
the  intermediate  points,  she  must  make  just  one 
revolution  on  her  axis  during  her  periodic  revolu- 
tion. At  A,  the  pillar  points  from  the  Sun,  and  at 
C  toward  him :  showing  that,  in  going  half-way 
round  the  Earth,  she  has  performed  half  a  revolu- 
tion upon  her  axis. 

416.  Though  the  Moon  always  presents  nearly  the  same  hemi- 
sphere toward  the  Earth,  it  is  not  always  precisely  the  same. 
Owing   to    the    ellipticity    of    her   orbit,    and    the   consequent 
inequality  of  her  angular  velocity,  she  appears  to  roll  a  little  on 
her  axis",  first  one  way  and  then  the  other — thus  alternately 
revealing  and  hiding  new  territory, 

as  it  were,  on  her  eastern  and  west-  ^^.^ 

ern  limbs.     This  rolling  motion  east  ...-  t) 

and  west  is  called  her  lilration  in  X         B 

Longitude.  fix. 


J 


/ 


MOON'S  LIBRATION. 


€>' 


The  accompanying  cut  will  illustrate  the  subject 
of  the  Moon's  Vibrations  in  longitude.  - 

From  A  around  to  C,  the  angular  motion  is 
slmcer  than  the  average,  and  the  diurnal  motion 
gains  upon  it,  so  that  the  pillar  points  west  of  the 
Earth,  and  we  see  more  of  the  eastern  limb  of  the 
moon. 

From  C  to  A,  again,  the  Moon  advances  faster 
than  a  mean  rate,  and  gains  upon  the  diurnal 
revolution ;  go  that  the  pillar  points  east  of  the 
Earth,  and  we  see  more  of  the  Moon's  western 
limb.  Thus  she  seems  *r  librate  or  roll,  first 
o  ie  way  and  then  ti.<;  other,  during  every  periodic 
re  volution. 

At  B,  we  see  most  of  her  eastern  limb  ;  and  at  D,  most  of  her  western. 

417.  The  axis  of  the  Moon  is  inclined  to  the  plane  of  her 
orbit  only  about  one  and  a  half  degrees  ( 1°  30'  1 0.8*}.     But  this 

415.  How  often  does  the  Moon  revolve  on  her  axis?     How  is  it  known  ?     What  follo-Td 
from  this  fact?        416.  What  are  the  Moon's  librations?    In   Lontfiiu.de?         4lT.  In 


210  ASTRONOMY. 

slight  inclination  enables  us  to  see  first  one  pole  and  then  the 
other,  in  her  revolution  around  the  Earth.  These  slight  rolling 
motions  are  called  her  librations  in  Latitude 

As  tne  inclination  of  the  Earth's  axis  brings  first  one  pole  and  then  the  other  toward  the 
Run,  and  produces  the  seasons,  so  the  inclination  of  the  Moon's  axis  brings  first  one  polo 
and  then  the  other  in  view  from  the  Earth.  But  as  her  inclination  ia  only  1J$°,  tho 
libration  in  latitude  is  very  slight. 

418.  "As  the  Moon  turns  on  her  axis  only  as  she  moves  around 
the  Earth,  it  is  plain  that  the  inhabitants  of  one  half  of  the 
lunar  world  are  totally  deprived  of  the  sight  of  the  Earth,  unless 
they  travel  to  the  opposite  hemisphere.     This  we  may  presume 
they  will  do,  were  it  only  to  view  so  sublime  a  spectacle  ;  for  it 
is  certain  that  from  the  Moon  the  Earth  appears  ten  times  larger 
than  any  other  body  in  the  universe. 

419.  As  the  Moon  enlightens  the  Earth,  by  reflecting  the  light 
of  the  Sun,  so  likewise  the  Earth  illuminates  the  Moon,  exhibit- 
ing to  her  the  same  phases  that  she  does  to  us,  only  in  a  con- 
trary order.     And,  as  the  surface  of  the  Earth  is  13  times  as 
large  as  the  surface  of  the  Moon,  the  Earth,  when  full  to  the 
Moon,  will  appear  13  times  as  large  as  the  full  Moon  does  to  us. 
That  side  of  the  Moon,  therefore,  which  is  towards  the  Earth, 
may  be  said  to  have  no  darkness  at  all,  the  Earth  constantly 
shining  upon  it  with  extraordinary  splendor  when  the  Sun  is 
absent  ;  it  therefore  enjoys  successively  two  weeks  of  illumina- 
tion from  the  Sun,  and  two  weeks  of  earth-light  from  the  Earth. 
The  other  side  of  the  Moon  has  alternately  a  fortnight's  light, 
and  a  fortnight's  darkness. 

420.  As  the  Earth  revolves  on  its  axis,  the  several  continents, 
seas,  and  islands,  appear  to  the  lunar  inhabitants  like  so  many 
spots  of  different  forms  and  brightness,  alternately  moving  over 
its  surface,  being  more  or  less  brilliant,  as  they  are  seen  through 
intervening  clouds.     By  these  spots,  the  lunarians  can  not  only 
determine  the  period  of  the  Earth's  rotation,  just  as  we  do  that 
of  the  Sun,  but  they  may  also  find  the  longitude  of  their  places, 
as  we  find  the  latitude  of  ours. 

421.  As  the  full  Moon  always  happens  when  the  Moon  is 
directly  opposite  the  Sun,  all  the  full  moon;:  in  our  winter,  must 
happen  when  the  Moon  is  on  the  north  side  of  tne  equinoctial, 

418.  Can  all  the  Lunarians  see  the  Earth?  How  large  must  she  appear  from  tht- 
Moon?  419.  What  said  of  her  light  and  phases  ?  How,  then,  are  the  two  hemispheres  of 
the  Moon  enlightened?  420.  How  must  the  Earth  appear  to  the  Lunarians,  and  what 
,  may  they  infer  from  the  motion  of  the  spots  seen  on  her  surface?  421.  W'.ere  is  the 
Moon  at  the  full  in  winter?  In  summer?  Why?  What  result  as  to  moonlighf  at  the 
poles  ? 


THE  MOON HER  MOTIONS,  PHASES,  ETC.      211 

because  then  the  Sun  is  on  the  south  side  of  it  ;  consequently,  at 
the  north  pole  of  the  Earth,  there  will  be  a  fortnight's  moon- 
light and  a  fortnight's  darkness  by  turns,  for  a  period  of  six 
months,  and  the  same  will  be  the  fact  during  the  Sun's  absence 
the  other  six  months,  at  the  south  pole. 

422.  The  plane  of  the  Moon's  orbit  is  very  near  that  of  the 
ecliptic.     It  departs  from  the  latter  only  about  5£°  (5°  8'  48W.) 

INCLINATION  OP  THB  MOON'S  ORBIT  TO  THE  PLANB  OF  THI  ECLIPTIC. 


Let  the  line  A  B  represent  the  plane  of  the  Earth's  orbit,  and  the  line  joining  the  Moon 
at  C  and  D  would  represent  the  inclination  of  the  Moon's  orbit  to  that  of  the  Earth.  At 
C  the  Moon  would  be  within  the  Earth's  orbit,  and  at  D  exterior  to  it ;  and  it  would  bo 
Full  Moon  at  D,  and  New  Moon  at  C. 

423.  The  Moon's  axis  being  inclined  only  about  1|-0  to  her 
orbit,  she  can  have  no  sensible  diversity  of  seasons  ;  from  which 
we  may  infer,  that  her  atmosphere  is  mild  and  uniform.     The 
quantity  of  light  which  we  derive  from  the  Moon  when  full,  is  at 
least  300,000  times  less  than  that  of  the  Sun. 

This  is  Monsieur  Bouquer's  inference,  from  his  experiments,  as  stated  by  La  Place,  in 
hii  work,  p.  42.  The  result  of  Dr.  Wollaston's  computations  was  different.  Professor 
Leslie  makes  the  light  of  the  Moon  150,000  times  less  than  that  of  the  Sun  ;  it  was  for- 
merly reckoned  100,000  times  less. 

424.  The  Moon,  though  apparently  as  large  as  the  Sun,  is  the 
smallest  of  all  the  heavenly  bodies  tmit  are  visible  to  the  naked 
eye.     Her  diameter  is  but  2162  miles  ;  consequently  her  surface 
is  13  times  less  than  that  of  the  Earth,  and  her  bulk  49  times 
less.     It  would  require  70,000,000  of  such  bodies  to  equal  the 
volume  of  the  Sun.     The  reason  why  she  appears  as  large  as  the 
Sun,  when,  in  truth,  she  is  so  much  less,  is  because  she  is  400 
times  nearer  to  us  than  the  Sun. 

425.  When  viewed  through  a  good  telescope,  the  Moon  pre- 
sents a  most  wonderful  and  interesting  aspect.      Besides  the 
large  dark  spots,  which  are  visible  to  the  naked  eye,  we  perceive 
extensive  valleys,  shelving  rocks,  and  long  ridges  of  elevated 
mountains,  projecting  their  shadows  on  the  plains  below.  Single 
mountains  occasionally  rise  to  a  great  height,  while  circular  hol- 
lows more  than  three  miles  deep,  seem  excavated  in  the  plains. 

422.  How  is  the  Moon's  orbit  situated  with  respect  to  the  ecliptic  ?  423.  What  is 
the  inclination  of  the  Moon's  axis,  and  what  effect  has  it  on  her  seasons  and  atmosphere  ? 
What  is  the  amount  of  light  derived  from  the  Moon  as  compared  with  the  Suu,  and  ib 
there  any  difference  of  opinion  on  this  point?  424.  What  said  of  the  apparent  and 
real  diameters  of  the  Moon?  Compared  with  the  Earth?  The  Sun?  Why,  then, 
appear  as  large  as  he  does  T  425.  How  does  she  appear  through  a  telescope  V  • 


212 


ASTRONOMY 


TELESCOPIC  VIEW  OF  THIS  MOON.  Specimens  of  these  shadows  may 

be  seen  in  the  cut,  projecting  to 
the  left.  Bright  points  of  light,  or, 
in  other  words,  the  illuminated 
tops  of  mountains,  may  also  be 
seen  near  the  terminator,  in  the 
dark  portion.  The  writer  has  often 
watched  them,  and  se«n  them  en- 
large more  and  more,  as  the  Sun 
arose  upon  the  side  of  the  Moon 
toward  us,  and  enlightened  the 
sides  of  her  mountains. 

The  shadows  are  always  pro- 
jected in  a  direction  opposite  the 
Sun,  or  towards  the  dark  side 
of  the  moon ;  and  as  her  eastern 
limb  is  dark  from  the  change  to  the 
full,  and  her  western  from  the  lull 
to  the  change,  of  course  the  direc- 
tion of  the  shadow*  must  be  re- 
versed. 

Suppose  a  person  stationed  at  a 
distance  directly  over  the  Andes. 
Before  the  Sun  arose,  he  would  see 
the  tallest  peaks  enlightened  ;  and 
as  he  arose,  the  long  shadows  of 
the  mountains  would  extend  to  tne 
west.  At  noon,  however,  little  or  no  shadow  would  be  visible  ;  but  at  sunset,  they  would 
again  be  s"een  stretching  away  to  the  east.  This  is  precisely  the  change  that  ic 
seen  to  take  place  with  the  lunar  shadows,  except  that  the  time  required  is  a  lunar  day, 
equal  to  about  15  of  our  days,  instead  of  one  of  our  days  of  12  hours. 

426.  The  Moon's  mountain  scenery  bears  a  striking  resem- 
blance to  the  towering  sublimity  and  terrific  ruggedness  of  the 
Alpine  regions,  or  of  the  Apennines,  after  which  some  of  her 
mountains  have  been  named,  and  of  the  Cordilleras  of  our  own 
continent.     Huge  masses  of  rock  rising  precipitously  from  the 
plains,  lift  their  peaked  summits  to  an  immense  height  in  the  air, 
while  shapeless  crags  hang  over  their  projecting  sides,  and  seem 
on  the  eve  of  being  precipitated  into  the  tremendous  chasm 
below. 

Around  the  base  of  these  frightful  eminences,  are  strewed 
numerous  loose  and  unconnected  fragments,  which  time  seems  to 
have  detached  from  their  parent  mass ;  and  when  we  examine 
the  rents  and  ravines  which  accompany  the  overhanging  cliffs, 
the  beholder  expects  every  moment  that  they  are  to  be  torn 
from  their  base,  and  that  the  process  of  destructive  separation 
which  he  had  only  contemplated  in  its  effects,  is  atfout  to  be 
exhibited  before  him  in  all  its  reality. 

427.  The  range  of  mountains  called  the  Apennines,  which 
traverses  a  portion  of  the  Moon's  disc  from  northeast  to  south- 
west, and  of  which  some  parts  are  visible  to  the  naked  eye,  rises 


426.  What  said  of  the  Moon's  mountain  scenery? 
T!cular  ? 


427.  Of  the  Apennines  in  nc,j 


THE  MOON HER  MOTIONS,  PHASES,  ETC       213 

with  a  precipitous  and  craggy  front  from  the  level  of  the  Mare 
Imbrium,  or  Sea  of  Showers.  In  this  extensive  range  are  several 
ridges  whose  summits  have  a  perpendicular  elevation  of  four 
miles,  and  more ;  and  though  they  often  descend  to  a  much 
lower  level,  they  present  an  inaccessible  barrier  on  the  northeast, 
while  on  the  southwest  they  sink  in  gentle  declivity  to  the 
plains. 

428.  There  is  one  remarkable  feature  in  the  Moon's  surface 
which  bears  no  analogy  to  anything  observable  on  the  Earth. 
This  is  the  circular  cavities  which  appear  in  every  part  of  her 
disc.     Some  of  these  immense  caverns  are  nearly  four  miles  deep, 
ana  forty  miles  in  diameter.     They  are  the  most  numerous  in  the 
southwestern    part.      As    they  reflect    the    Sun's    rays  more 
copiously,  they  render  this  part  of  her  surface  more  brilliant 
than  any  other.     They  present  to  us  nearly  the  same  appearance 
as  our  Earth  might   be  supposed  to  present  to  the  Moon  if  all 
our  great  lakes  and  seas  were  dried  up. 

429.  The  number  of  remarkable  spots  on  the  Moon,  whose 
latitude  and  longitude  have  been  accurately  determined,  exceeds 
200.     The  number  of  seas  and  lakes,  as  they  were  formerly  con- 
sidered, whose  length  and  breadth  are  known,  is  between  20  and 
30  ;  while  the  number  of  peaks  and  mountains,  whose  perpen- 
dicular elevation  varies  from  a  fourth  of  a  mile  to  five  miles  in 
height,  and  whose  bases  are  from  one  to  seventy  miles  in  length 
is  not  less  than  one  hundred  and  fifty. 

Graphical  views  of  these  natural  appearances,  accompanied  with  minute  and  familiar 
descriptions,  constitute  what  is  called  Selenography,  from  two  Greek  words,  which  mean 
the  same  thing  in  regard  to  the  Moon,  as  Geography  does  in  regard  to  the  Earth. 

430.  An  idea  of  some  of  these  scenes  may  be  formed  by  con- 
ceiving a  plane  of  about  100  miles  in  circumference,  encircled  by 
a  range  of  mountains,  of  various  forms,  three  miles  in  perpen- 
dicular height,  and  having  a  mountain  near  the  center,  whose 
top  reaches  a  mile  and  a  half  above  the  level  of  the  plain.     From 
the  top  of  this  central  mountain,  the  whole  plain,  with  all  its 
scenery,   would   be  distinctly  visible,   and  the  view  would  be 
bounded  only  by  a  lofty  amphitheatre  of  mountains,  rearing  their 
summits  to  the  sky. 

431.  The  bright  spots  of  the   Moon   are   the  mountainous 
regions  ;  while* the  dark  spots  are  the  plains,  or  more  level  parts 
of  her  surface.     There  may  be  rivers  or  small  lakes  on  this 


428.  What  remarkable  feature  of  the  Moon's  surface  noticed  ?  429.  What  numboi 
f  remark-able  spots  ?  Of  "  seas  or  lakes  ?  "  Of  mountains  ?  What  is  Selenography  ? 
C»\  Uc-v  uonceive  jurtly  of  the  lunar  scenery?  481.  What  are  the  brightest  spota  oo 


214  ASTRONOMY. 

planet ;  but  it  is  generally  thought,  by  astronomers  of  the  presen* 
"day,  that  there  are  no  seas  or  large  collections  of  water,  as  was 
formerly  supposed.  Some  of  these  mountains  and  deep  valley? 
are  visible  to  the  naked  eye  ;  and  many  more  are  visible  through 
a  telescope  of  but  moderate  powers. 

432.  A  telescope  which  magnifies  only  100  times  will  show  a 
spot  on  the  Moon's  surface,  whose  diameter  is  1223  yards ;  ana 
one  which  magnifies  a  thousand  times,  will  enable  us  to  perceive 
any  enlightened  object  on  her  surface  whose  dimensions  are  only 
122  yards,  which  does  not  much  exceed  the  dimensions  of  some 
of  our  public  edifices,  as  for  instance,  the  Capitol  at  Washington, 
or  St.  Paul's  Cathedral.  Some  years  since,  Professor  Frauen- 
hofer,  of  Munich,  announced  that  he  had  discovered  a  lunar 
edifice,  resembling  a  fortification,  together  with  several  lines  of 
road.  The  celebrated  astronomer  Schroeter,  conjectures  the 
existence  of  a  great  city  on  the  east  side  of  the  Moon,  a  little 
north  of  her  equator,  an  extensive  canal  in  another  place,  and 
fields  of  vegetation  ir  another. 


CHAPTER  Y. 

SOLAR    AND   LUNAR   ECLIPSES. 

483.  OF  all  the  phenomena  of  the  heavens,  there  are  none 
which  engage  the  attention  of  mankind  more  than  eclipses  of  the 
Sun  and  Moon  ;  and  to  those  who  are  unacquainted  with  astro- 
nomy, nothing  appears  more  wonderful  than  the  accuracy  with 
which  they  can  be  predicted.  In  the  early  ages  of  antiquity, 
they  were  regarded  as  alarming  deviations  from  the  established 
laws  of  nature,  presaging  great  public  calamities,  and  other 
tokens  of  the  divine  displeasure. 

In  China,  the  prediction  and  observance  of  eclipses  are  made  a  matter  of  state  policy, 
in  order  to  operate  upon  the  fears  of  the  ignorant,  and  impose  on  them  a  superstitioun 
regard  for  the  occult  wisdom  of  their  rulers.  In  Mexico,  the  natives  fast  and  afflict  ttiem- 
selves,  during  eclipses,  under  an  apprehension  that  the  Great  Spirits  in  deep  sufferance. 
Some  of  the  northern  tribes  of  Indians  have  imagined  that  the  Moon  had  been  wounded 
in  a  quarrel ;  and  others,  that  she  was  about  to  be  swallowed  by  a  hpge  fish. 

the  Moon's  surface?  The  dark  ones?  432.  How  small  objects  maybe  seen  ou  tho 
Moon's  surface?  What  announcement  by  Frauenhofer?  Conjecture  of  Srhroeter  ( 
488.  Subject  of  Chapter  V.?  Remark  respecting  eclipses?  How  regarded  by  tic 
ancients?  In  China?  Mexico?  By  northern  Indians?  Anecdote  of  Columbus 9 


SOLAR    AND    LUNAR    ECLIPSES.  215 

It  was  by  availing  himself  of  these  superstitious  notions,  that  Columbus,  when  ship- 
wrecked on  the  island  of  Jamaica,  extricated  himself  and  crew  from  a  most  embarrass- 
ing condition.  Being  driven  to  great  distress  for  want  of  provisions,  and  the  natives 
refusing  him  any  assistance,  when  all  hope  seemed  to  be  cut  off,  he  bethought  himself  of 
their  superstition  in  regard  to  eclipses.  Having  assembled  the  principal  men  of  the 
island,  he  remonstrated  against  their  inhumanity,  as  being  offensive  to  the  Great  Spirit  : 
and  told  them  that  a  great  plague  was  even  then  ready  to  fall  upon  them,  and  as  a  token 
of  it,  they  would  that  night  see  the  Moon  hide  her  face  in  anger,  and  put  on  a  dreadfully 
dark  and  threatening  aspect.  This  artifice  had  the  desired  effect;  for  the  eclipse  had  no 
nooner  begun,  than  the  frightened  barbarians  came  running  with  all  kinds  of  provisions, 
and  throwing  themselves  at  the  feet  of  Columbus,  implored  his  forgiveness.— Almagest, 
vol.  /.,  55  c.  v.  2. 

434.  An  eclipse  of  the  Sun  takes  place,  when  the  dark  body 
of  the  Moon,  passing  directly  between  the  Earth  and  the  Sun, 
intercepts  his  light.     This  can  happen  only  at  the  instant  of  new 
rnoon,  or  when  the  Moon  is  in  conjunction ;  for  it  is  only  then 
that  she  passes  between  us  and  the  Sun. 

An  eclipse  of  the  Moon  takes  place  when  the  dark  body  of 
the  Earth,  coming  between  her  and  the  Sun,  intercepts  his  light, 
and  throws  a  shadow  on  the  Moon.  This  can  happen  only  at  the 
time  of  full  moon,  or  when  the  Moon  is  in  opposition  ;  for  it  is 
only  then  that  the  Earth  is  between  her  and  the  Sun. 

435.  As  every  planet  belonging  to  the  solar  system,  both  pri- 
mary and  secondary,  derives  i4s  light  from  the  Sun,  it  must  cast 
a  shadow  towards  that  part  of  the  heavens  which  is  opposite  to 
the  Sun.     If  the  Sun  and  planet  were  both  of  the  same  magni- 
tude, the  form  of  the  shadow  cast  by  the  planej:,  would  be  that 
of  a  cylinder,  and  of  the  same  diameter  as  the  Sun  or  planet. 

CYLINDRICAL  SHADOW. 


Here  the  Sun  and  planet  are  represented  as  of  tlie  same  size,  and  the  shadow  of  the 
latter  is  in  the  form  of  a  cylinder. 

436.  If  the  planet  were  larger  than  the  Sun,  the  shadow  would 
continually  diverge,  and  grow  larger  and  larger  ;  but  as  the  Sun 
is  much  larger  than  any  of  the  planets,  the  shadows  which  they 
cast  must  converge  to  a  point  in  the  form  of  a  cone,  the  length 
of  which  will  be  proportional  to  the  size  and  distance  of  the 
planet  from  the  Sun. 

434.  When  do  solar  eclipses  occur?  Why  only  then?  Lunar?  Why  only  at  full 
moon  ?  435.  Do  all  the  planets  cast  shadows  ?  Suppose  the  Sun  and  planet  were  of 
the.  same  size,  what  would  be  the  form  of  their  shadows?  436.  What  if  the  planet  waa 
largest  ?  How  as  they  are  smaller  than  the  Sun  ?  How  is  the  length  of  the  shadov 
modified  bj  the  distance  of  the  planet  from  the  Sun  ? 


ASTRONOMY. 


DIVERGING  SHADOW. 


In  this  cut,  the  opaque  body  is  ttie  larger,  and  the  ^ide°^rojected  fr°m  lt  dt9°       *» 
point. 

CONVERGING  SHADOW. 


Here  the  luminous  body  is  the  larger,  and  the  shadow  converges  to  a  n^int,  and  t*  IB 
the  form  of  a  cone. 

The  opaque  body  being  smaller  than  the  luminous  one,  the  length,  of  its  shadow  will  o 
modified  by  its  distance,  as  in  the  following : 


Here,  also,  the  luminous  body  is  the  larger,  and  both  precisely  or  the  ff.me  size  as  1 
the  cut  preceding ;  but  teing  placed  nearer  each  other,  the  shadow  is  shown  to  be  cor 
siderably  shorter. 

437.  All  the  planets,  both  primaries  and  secondaries,  cas 
shadows  in  a  direction  opposite  the  Sun  (see  cut  on  i?ext  page) 
The  form  and  length  of  these  shadows  depend  upon  the  compare 
tive  magnitude  of  the  Sun  and  planet,  and  their  distance  from 
each  other.  If  the  Sun  and  a  planet  were  of  the  same  size,  the 
shadow  of  the  planet  would  be  in  the  form  of  a  cylinder,  what- 
ever its  distance.  If  the  planet  was  larger  than  the  Sun,  the 
shadow  would  diverge,  as  we  proceed  from  the  planet  off  into 
space  ;  and  the  nearer  the  Sun,  the  more  divergent  the  shadow 
would  be.  But  as  the  planets  are  all  much  smaller  than  the 
Sun,  the  shadows  all  converge  to  a  point,  and  take  the  form  of  a 
cone;  and  the  nearer' to  the  Sun,  the  shorter  their  shadows. 


437.  Why  have  the  largest  and  most  distant  planets  the  longest  shadows  ?    Do  Any  of 
fce  primary  planets  eclipse  each  other? 


SOLAR    AND    LUNAR    ECLIPSES 


217 


SHADOWS  OF  THE   PLANETS. 


These  principles  are  partly  illus- 
trated in  the  adjoining  cut.  The 
planets  nearest  the  Sun  have  com- 
paratively short  shadows,  while  those 
more  remote  extend  to  a  great  dis- 
tance. No  primary,  however,  casts  a 
shadow  long  enough  to  reach  the  next 
exterior  planet. 

The  magnitude  of  the  Sun  is  such, 
that  the  shadow  cast  by  each  of  the 
primary  planets  always  converges  to 
a  point  before  it  reaches  any  other 
planet;  so  that  not  one  of  the  pri- 
mary planets  can  eclipse  another. 
The  shadow  of  any  planet  which  is 
accompanied  by  Satellites,  may,  on 
certain  occasions,  ec'ipse  its  satel- 
lites ;  but  it  is  not  long  enough  to 
eclipse  any  other  body.  The  shadow 
of  a  satellite  or  Moon,  may  also,  on 
certain  occasions,  fall  on  the  primary, 
and  eclipse  it. 


438.  When  the  Sun  is  at  his  greatest  distance  from  the  Earth, 
and  the  Moon  at  her  least  distance,  her  shadow  is  sufficiently 
long  to  reach  the   Earth,   and   extend    19,000   miles   beyond. 
When  tbe  Sun  is  at  his  least  distance  from  the  Earth,  and  the 
Moon  at  her  greatest,  her  shadow  will  not  reach  the  Earth's  sur- 
face by  20,000  miles.     So  that  when  the  Sun  and  Moon  are  at 
their  mean  distances,  the  cone  of  the  Moon's  shadow  will  termi- 
nate a  little  before  it  reaches  the  Earth's  surface. 

In  the  former  case,  if  a  conjunction  take  place  when  the  center  of  the  Moon  comes  in  a 
direct  line  between  the  centers  of  the  Sun  and  Earth,  the  dark  shadow  of  the  Moon  will 
fall  centrally  upon  the  Earth,  and  cover  a  circular  area  of  175  miles  in  diameter.  To  all 
places  lying  within  this  dark  spot,  the  Sun  will  be  totally  eclipsed,  as  illustrated  by  the 
figure. 

439.  Eclipses  of  the  Sun  must  always  happen  at  New  Moon, 
and  those  of  the  Moon  at  Full  Moon.     The  reason  of  this  is, 
that  the  Moon  can  never  be  between  us  and  the  Sun,  to  eclipse 
him,  except  at  the  time  of  her  change,  or  New  Moon  ;  and  she 
can  never  get  into  the  Earth's  shadow,  to  be  eclipsed  herself, 
except  when  she  is  in  opposition  to  the  Sun,  and  it  is  Full 
Moon 

440.  If  the  Moon's  orbit  lay  exactly  in  the  plane  of  the  eclip- 
tic, she  would  eclipse  the  Sun  at  every  change,  and  be  eclipsed 
herself  at  every  full ;  but  as  her  orbit  departs  from  the  ecliptic 
over  5°  (422),  she  may  pass  either  above  or  below  the  Sun  at 

438.  What  is  the  length  of  the  Moon's  shadow  when  she  is  nearest  the  Earth  and 
farthest  from  the  Sun?  What  when  nearest  the  Sun  and  farthest  from  the  Earth? 
What  when  the  Sun  and  Moon  are  at  their  mean  distances?  439.  At  wha'  time  of  the 
Moou  oo  bolar  eclipses  always  occur?  Lunar?  Why?  440.  Why  not  two  solar  an<l 


SJJ8 


ASTRONOMY 


the  time  of  her  change,  or  above  or  below  the  Earth's  shadow 
at  the  time  of  her  full. 


NEW   AND   FULL  MOONS  WITHOUT   ECLIPSES. 

ow  above  tile  Earth.  Above  the  Earth's  shadow. 


Shadow  below  the  Earth. 


Below  the  Earth's  shadow. 


Let  the  line  joining  the  Earth  and  the  Sun  represent  the  plane  of  the  ecliptic.  Now  as 
tae  orbit  of  the  Moon  departs  from  this  plane  about  5°  9',  she  may  appear  either  above 
or  below  the  Sun  at  New  Moon,  as  represented  in  the  figure,  and  her  shadow  may  fall 
above  the  north  pole  or  below  the  south.  At  such  times,  then,  there  can  be  no  solar 
eclipse. 

On  the  right,  the  Moon  is  shown  at  her  full,  both  above  and  below  the  Earth's  shadow, 
in  which  case  there  can  be  no  lunar  eclipse. 

441.  As  the  Moon  passes  from  one  of  her  nodes  to  the  other 
in  173  days,  there  is  just  this  period  between  two  successive 
eclipses  of  the  Sun,  or  of  the  Moon.     In  whatever  time  of  the 
year,  then,  we  have  eclipses  at  either  node,  we  may  be  sure  that 
in  173  days %after wards,  we  shall  have  eclipses  at  the  other  node. 

As  the  Moon's  nodes  fall  back,  or  retrograde  in  the  ecliptic,  at  the  rate  of  19J6°  every 
year,  they  will  complete  a  backward  revolution  entirely  around  the  ecliptic  to  the  same 
point  again,  in  18  years,  225  days  ;  in  which  time  there  would  always  be  a  regular  period 
of  eclipses,  if  any  complete  number  of  lunations  were  finished  without  a  remainder.  But 
this  never  happens ;  for  if  both  the  Sun  and  Moon  should  start  from  a  line  of  conjunction 
with  either  of  the  nodes  in  any  point  of  the  ecliptic,  the  Sun  would  perform  IS  annual 
revolutions  and  222°  of  another,  while  the  Moon  would  perform  230  lunations,  and  85°  of 
another,  before  the  node  would  come  around  to  the  same  point  of  the  ecliptic  again  ;  so 
that  the  Sun  would  then  be  138*  from  the  node,  and  the  Moon  85°  from  the  Sun. 

But  after  228  lunations,  or  18  years,  11  days,  7  hours,  42  minutes,  and  81  seconds,  the 
Bun,  Moon,  and  Earth,  will  return  so  nearly  in  the  same  position  with  respect  to  each 
other,  that  there  will  be  a  regular  return  of  the  same  eclipses  for  many  ages.  This 
grand  period  was  discovered  by  the  Chaldeans,  and  by  them  called  Saros.  If,  therefore, 
to  the  mean  time  of  any  eclipse,  either  of  the  Sun  or  Moon,  we  add  the  Chaldean  period 
of  JS  years  and  11  days,  we  shall  have  the  return  of  the  same  eclipse.  This  mode  of  pre- 
dicting eclipses  will  hold  good  for  a  thousand  years.  In  this  period  there  are  usually  70 
eclipses ;  41  of  the  Sun  and  29  of  the  Moon 

442.  The  diameter  of  the  Earth's  shadow,  at  the  distance  of 
the  Moon,  is  nearly  three  times  as  large  as  the  diameter  of  the 
Moon  ;  and  the  length  of  the  Earth's  shadow  is  nearly  four  times 
as  great  as  the  distance  of  the  Moon  ;  exceeding  it  in  the  same 
ratio  that  the  diameter  of  the  Earth  does  the  diameter  of  the 
Moon;  which  is  as  3.663  to  1. 

443.  The  number  of  eclipses  in  any  one  year,  cannot  be  less 
than  two,  nor  more  than  seven.     In  the  former  case,  they  will 

two  lunar  eclipses  every  lunar  month?  441.  How  often  may  eclipses  occur  at  oppo- 
site nodes?  What  cycle  of  eclipses  described?  Number  of  eclipses  in  this  cycle? 
442.  What  is  the  diameter  of  the  Earth's  shadow  at  the  distance  of  the  Moon?  443. 
What  nuuiber  of  eclipses  may  occur  in  any  one  year?  If  but  two,  what  will  they  be? 


SOLAR    AND    LUNAR    ECLIPSES. 


19 


both  be  of  the  Sun  ;  and  in  the  latter,  there  will  be  five  of  the 
Sun,  and  two  of  the  Moon — those  of  the  Moon  will  be  total. 
There  are  sometimes  six  ;  but  the  usual  number  is  four  :  two  of 
the  Sun,  and  two  of  the  Moon. 

The  cause  of  this  variety  is  thus  accounted  for.  Although  the  Sun  usually  passes 
by  both  nodes  only  ouce  ia  a  year,  he  may  pass  the  same  node  again  a  little  beforo 
the  end  of  the  year.  In  consequence  of  the  retrograde  motion  of  the  Moon's  nodes, 
he  will  come  to  either  of  them  173  days  after  passing  the  other.  He  may,  there 
fore,  return  to  the  same  node  in  about  846  days,  having  thus  passed  one  node  twice,  and 
the  other  once,  making  each  time,  at  each,  an  eclipse  of  both  the  Sun  and  the  Moon,  or 
kijs  h.  all.  And  since  12  lunations,  or  354  days  from  the  first  eclipse,  in  the  beginning  of 
Hie  yt.ar,  leave  room  for  another  New  Moon  before  the  close  of  the  year,  and  since  this 
New  Moon  may  fall  within  the  ecliptic  limit,  it  is  possible  for  the  Sun  to  be  eclipsed  again. 
Tims  there  may  be  seven  eclipses  in  the  same  year. 

444.  Eclipses  of  the  Sun  always  come  on  from  the  west,  and 
pass  over  eastward  ;  while  eclipses  of  the  Moon  come  on  from 

LUNA,  KCUPSB.    *c.  east>  arld  V™*  over  westward.    SOLAR  ECL[PSE 
This  is  a  necessary  result  of  the 
eastward  motion  of  the  Moon  in 
her  orbit. 

In  the  right  hand  cut,  the  Moon  is  seen 
revolving  eastward,  throwing  her  shadow  upon 
the  Earth,  and  hiding  the  western  limb  of  the 
Sun.  In  some  instances,  however,  when  the 
eclipse  is  very  slight,  it  may  first  appear  on  the 
northern  or  southern  limb  of  the  Sun — that  is, 
the  upper  or  lower  side;  but  even  then  its 
direction  must  be  from  west  to  east.  It  will 
also  be  obvious  from  this  figure,  that  the  sha- 
dow of  the  Moon  upon  the  Earth  must  also  tra- 
verse her  surface  from  west  to  east ;  conse- 
quently the  eclipse  will  be  visible  earlier  in  the 
west  than  in  the  east. 

On  the  left,  the  Moon  is  seen  striking  into 
the  Earth's  shadow  from  the  west,  and  having 
her  eastern  limb  first  obscured.  By  holding  the 
book  up  south  of  him,  the  student  will  see  at 
once  why  the  revolution  of  the  Moon  eastward 
must  cause  a  solar  eclipse  to  proceed  from  west 
to  east,  and  a  lunar  eclipse  from  east  to  west. 
To  locate  objects  and  motions  correctly,  the 
student  should  generally  imagine  himself  look- 
ing to  the  south,  as  we  are  situated  north  of  the 
equinoctial.  The  student  should  bear  in  mind 
that  nearly  all  the  cuts  in  the  boik  are  drawn 
to  represent  a  view  from  northern  latitude 
upon  the  Earth.  Hence,  by  holding  the  book 
up  south  of  him,  the  cuts  will  generally  afford 
an  accurate  illustration  both  of  the  positions 
and  motions  of  the  bodies  represented. 

445.  The  time  which  elapses  between  two  successive  changes 
of  the  Moon  is  called  a  Lunation,  which,  at  a  mean  rate,  is  about 


If  seven?  What  is  the  usual  number?  Can  you  explain  the  cause  of  this  variety  P 
444.  What  is  the  direction  of  a  solar  eclipse?  A  lunar?  Why  this  difference?  445. 
Whtit  is  a  Itmalionf  What  would  be  the  effect  if  the  solar  and  lunar  months  w<.ro 
What  result  from  the  existing  inequality? 


B.G. 


10 


ASTRONOMY. 

29^  days.  If  12  lunar  months  were  exactly  equal  to  the  12  solar 
months,  the  Moon's  nodes  would  always  occupy  the  same  pointy 
in  the  ecliptic,  and  all  eclipses  would  happen  in  the  same  months 
of  the  year,  as  is  the  case  with  the  transits  of  Mercury  and 
Yenus  :  but,  in  12  lunations,  or  lunar  months,  there  are  only 
354  days  ;  and  in  this  time  the  Moon  has  passed  through  both 
her  nodes,  but  has  not  quite  accomplished  her  revolution  around 
the  Sun  ;  the  consequence  is,  that  the  Moon's  nodes  fall  back  iu 
the  ecliptic  at  the  rate  of  about  19^°  annually  ;  so  that  the 
eclipses  happen  sooner  every  year  by  about  19  days. 

446.  Eclipses  can  never  take  place,  except  when  the  Moon 
is  near  the  ecliptic  ;  or,  in  other  words,  at  or  near  one  of  her 
nodes.  At  all  other  times,  she  passes  above  or  below  the  Sun, 
and  also  above  or  below  the  Earth's  shadow.  It  is  not  neces- 
sary that  she  should  be  exactly  at  her  node,  in  order  that  an 
eclipse  occur.  If  she  is  within  17°  of  her  node,  at  the  time  of 
her  change,  she  will  eclipse  the  Sun  ;  and  if  within  12°  of  her 
node  at  her  full,  she  will  strike  into  the  Eariii's  shadow,  and  be 
more  or  less  eclipsed.  These  distances  are  called,  respectively, 
the  solar  and  lunar  ecliptic  limits. 

This  subject  may  be  understood  by  consulting  the  following  figure . 

THE    MOON    CHANGING    AT    DIFFERENT    DISTANCES    FROM    HER   NODES. 

Let  the  line  E  E  represent  the  ecliptic,  and  the  line  0  0  the  plane  of  the  Moon's 
.orbit.  The  light  globes  are  the  Sun,  and  the  dark  ones  the  Moon,  which  may  be  imagined 
as  much  nearer  the  student ;  hence  their  apparent  diameter  is  the  same. 

Let  the  point  A,  represent  the  node  of  the  Moon's  orbit.  Now  if  the  change  occur 
when  the  Moon  is  at  B,  she  will  pass  bflcnc  the  Sun.  If  when  at  C,  she  will  just  touch  hia 
lower  limb.  At  C,  she  will  eclipse  him  a  little,  and  so  on  to  A;  at  which  point,  if  the 
change  occurs,  the  eclipse  would  be  central,  and  probably  total. 

If  the  Moon  was  at  Gr,  H,  I,  or  J,  in  her  orbit,  when  the  change  occurred,  she  would 
eclipse  the  upper  or  northern  limb  of  the  Sun,  according  to  her  distance  from  her  node 
at  the  time  ;  but  if  she  was  at  K,  she  would  pass  above  the  Sun,  and  would  not  eclipse 
him  at  all.  The  points  C  and  J  will  represent  the  Solar  Ecliptic  Limits. 

The  mean  ecliptic  limit  for  the  Sun  is  16}^°  on  each  side  of  the  node  ;  the  mean  eclip- 
tic limit  for  the  Moon  is  10,^°  on  each  side  of  the  node.  In  the  former  case,  then,  there 
are  33  degrees  about  each  node,  making,  in  all,  66°  out  of  860°,  in  which  eclipses  of  the 
Sun  may  happen  ;  in  the  latter  case  there  are  21°  about  each  node,  making,  in  all,  42* 
out  of  360°  in  which  eclipses  of  the  Moon  usually  occur.  The  proportion  of  the  solar  to 
the  lunar  eclipses,  therefore,  is  as  66  to  42,  or  as  11  to  7.  Yet,  there  are  more  visible 
*=ulipses  of  the  Moon,  at  any  given  place,  than  of  the  Sun  ;  because  a  lunar  eclipse  id 
visible  to  a  whole  hemisphere,  a  solar  eclipse  only  to  a  small  portion  of  it. 

447.  All  parts  of  a  planet's  shadow  are  not  alike  dense.     The 

4-1(5.  Where  must  the  Moon  be,  with  respect  to  the  ecliptic  and  her  nodes,  in  order  to 
an  eclipse?  What  meant  by  ecliptic  Urn  UK  ?  Name  the  distance  of  each,  respectively, 
from  the  node.  Illustrate.  447.  What  is  the  umbra  of  the  Earth  or  Moon?  The 


SOLAR    AND    LUNAR    ECLIPSES.  221 

darkest  portion  is  called  the  umbra,  and  the  partial  shadow  the 
penumbra. 

UMBRA    AND   PC1TTTHBRA   CF  THE   EARTH   AND   MOOS. 


Penumbra  is  from  the  Latin  pene,  almost,  and  ivrribra,  a  shadow.  In  this  cut,  the 
Earth's  umbra  and  penumbra  will  be  readily  found  by  the  lettering  ;  while  A  is  the  umbra, 
and  B  B  the  penumbra,  of  the  Moon.  The  latter  is  more  broad  than  it  should  be,  owing 
to  the  nearness  of  the  Sun  in  the  cut,  as  it  never  extends  to  much  over  half  the  Earth's 
diameter.  The  student  will  see  at  once  that  solar  eclipses  can  be  total  only  to  persons 
Tithin  the  umbra ;  while  to  all  on  which  the  penumbra  falls,  a  portion  of  the  Sun's  disc 
will  be  obscured. 

448.  The   average   length   of   the    Earth's   umbra   is  about 
860,000  miles  ;  and  its  breadth,  at  the  distance  of  the  Moon,  is 
about  6500  miles,  or  three  times  the  Moon's  diameter. 

As  both  the  Earth  and  Moon  revolve  in  elliptical  orbits,  both  the  above  estimates  are 
subject  to  variations.  The  length  of  the  Earth's  umbra  varies  from  842,217  to  871,262 
miles  ;  and  its  diameter,  where  the  moon  passes  it,  varies  from  5235  to  6365  miles. 

449.  The   average   length   of   the   Moon's   umbra   is   about 
239,000   miles.      It   varies   from   221,148    to    252,638    miles, 
according  to  the  Moon's  distance  from  the  Sun.     Its  greatest 
diameter,  at  the  distance  of  the  Earth,  is   ItO  miles  ;  but  the 
yenumbra  may  cover  a  space  on  the  Earth's  surface  4393  miles 
in  diameter. 

When  the  Moon  but  just  touches  the^imb  of  the  Sun,  or  the 
umbra  of  the  Earth,  it  is  called  an  appulse  (see  C  and  J  in  the 
cut  on  the  opposite  page). 

450.  A  partial  eclipse  is  one  in  which  only  part  of  the  Sun  or 
Moon   is   obscured.     A  solar   eclipse   is  partial  to   all   places 
outside  the  umbra  ;  but  within  the  umbra,   where  the  whole 
disc  is  obscured,  the  eclipse  is  said  to  be  total.     A  central  eclipse 
is  one  taking  place  when  the  Moon  is  exactly  at  one  of  her  nodes. 
If  lunar,  it  is  total,  as  the  Earth's  umbra  is  always  broad  enough, 
at  the  Moon's  distance,  if  centrally  passed,  to  obscure  her  whole 
disc.     But  a  solar  eclipse  may  be  central  and  not  total,  as  the 
Moon  is  not  always  of  sufficient  apparent  diameter  to  cover  the 

Henumbraf  Derivation?  Within  which  are  solar  eclipses  total?  448.  The  average 
length  of  the  Earth's  shadow?  Breadth  at  the  Moon's  distance?  Do  they  vary?  Why? 
i49.  Average  length  of  the  Moon's  umbra?  Does  it  vary  ?  Why?  Greatest  diameter 
at  the  Earth's  surface?  Of  penumbra?  What  is  an  appulse f  450.  A  par-tint 
eclipse?  Atotalf  ^.central?  Are  all  centra) 'tclinses  total?  Why  not?  What  calh-d 
then?  Why? 


222 


ASTRONOMY. 


whole  disc  of  the  Sun.  In  that  case,  the  eclipse  would  be 
annular  (from  annulus,  a  ring),  because  the  Moon  only  hides  the 
center  of  the  Sun,  and  leaves  a  bright  ring  unobscured. 


Going  o3. 


PROGRESS  OF  A    CENTRAL  ECLIPSE. 

Annular. 


Coming  ou. 


451.  It  has  already  been  shown  that  the  apparent  magni- 
tudes of  bodies  vary  as  their  distances  vary ;  and  as  both  the 
Earth  and  Moon  revolve  in  elliptical  orbits,  it  follows  that  the 
Moon  and  Sun  must  both  vary  in  their  respective  apparent  mag- 
nitudes. Hence  some  central  eclipses  of  the  Sun  are  total, 
while  others  are  partial  and  annular. 


TOTAL  AND  ANNULAR  ECLIPSES  OF  THE  SUN 


At  A,  the  Earth  is  at  her  aphelion,  and  the  Sun  being  at  his  most  distant  point,  will 
fiave  his  least  apparent  magnitude.  At  the  same  time,  the  Moon  is  in  perigee,  and 
appears  larger  than  usual.  If,  therefore,  she  pass  centrally  over  the  Sun's  disc,  tho 
eclipse  will  be  total. 

At  B,  this  "order  is  reversed.  The  Earth  is  at  her  perihelion,  and  the  Moon  in  apogee; 
so  that  the  Sun  appears  larger,  and  the  Moon  smaller  than  usual.  If,  then,  a  central 
eclipse  occur  under  these  circumstances,  the  Moon  will  not  be  large  enough  to  eclipse  the 
whole  of  the  Sun,  but  will  leave  a  ring,  apparently  around  herself,  unobscured.  Such 
eclipse  will  be  annular. 

452.  The  greatest  possible  duration  of  the  annular  appearance 
of  a  solar  eclipse,  is  12  minutes  and  24  seconds;  and  the  greatest 
possible  time  during  which  the  Sun  can  be  totally  eclipsed,  to 
any  part  of  the  world,  is  7  minutes  and  58  seconds.  The  Moon 
may  continue  totally  eclipsed  for  one  hour  and  three  quarters. 

553.  As  the  solar  ecliptic's  limits  are  further  from  the  Moon's 
nodes  than  the  lunar,  it  results  that  we  have  more  eclipses  of 
the  Sun  than  of  the  Moon.  There  may  be  seven  in  all  in  one 

451.  Why  are  buu.3  central  eclipses  total,  and  others  partial  and  annular?  452. 
How  long  may  an  annului  eclipse  continue  ?  A  total  eclipse  of  the  Sun  ?  Of  the  Moon? 
453.  Which  kind  of  eclipses  is  most  frequent?  Why?  The  greatest  number  in  a  year  f 


SOLAR    AND    LUNAR    ECLIPSES.  223 

year,  viz.,  five  solar  and  two  lunar  ;  but  the  most  asual  number 
is  four.  There  can  never  be  less  than  two  in  a  year  ;  in  which 
case,  both  must  be  of  the  Sun.  Eclipses  both  of  the  Sun  and 
Moon  recur  in  nearly  the  same  order,  and  at  the  same  intervals, 
at  the  expiration  of  a  cycle  of  223  lunations,  or  18  years  of  365 
days  and  15  hours.  This  cycle  is  called  the  Period  of  the 
Eclipses.  At  the  expiration  of  this  time,  the  Sun  and  the 
Moon's  nodes  will  sustain  the  same  relation  to  each  other  as  at 
the  beginning,  and  a  new  cycle  of  eclipses  begins. 

454.  In  a  total  eclipse  of  the  Sun,  the  heavens  are  shrouded 
in  darkness,  the  planets  and  stars  become  visible,  the  tempera- 
ture declines,  the  animal  tribes  become  agitated,  and  a  general 
gloom  overspreads  the  landscape.     Such  were  the  effects  of  the 
great  eclipse  of  1806.     In  a  lunar  eclipse,  the  Moon  begins  to 
lose  a  portion  of  her  light  and  grows  dim,  as  she  enters  the 
Earth's  penumbra,  till  at  length  she  comes  in  contact  with  the 
umbra,  and  the  real  eclipse  begins. 

455.  In  order  to  measure  and  record  the  extent  of  eclipses, 
the  apparent  diameters  of  the  Sun  and  Moon  are  divided  into 
twelve  equal  parts,  called  digits;    and  in  predicting  eclipses, 
astronomers  usually  state  which  "limb"  of  the  body  is  to  be 
eclipsed — the  southern  or  northern — the  time  of  thd  first  con- 
tact, of  the  nearest  approach  of  centers,  direction,  And  number 
of  digits  eclipsed. 

FIVE  DIGITS  ECLIPSED.  TWELVE  DIGITS.  «, 


456.  The  last  annular  eclipse  visible  in  the  United  States, 
occurred  May  26,  1854.  The  next  total  eclipse  of  the  Sun  will 
be  August  7,  1869. 

Some  of  the  ancients,  and  all  barbarous  nations,  formerly 
regarded  eclipses  with  amazement  and  fear,  as  uupernaturul 
events,  indicating  the  displeasure  of  the  gods.  Cc  ambus  is  said 

How  many  of  each?  Least  number,  and  which?  Usual  number?  What  said  of  the 
order  of  eclipses?  Time  of  cycle?  454.  Describe  the  effects  of  t  total  eclipse  of  the 
Sun.  The  process  of  a  lunar  eclipse?  455.  How  are  eclipses  measured  and  recorded? 
456.  When  the  next  annular  eclipse  visible  in  this  country  ?  The  neat  total?  How  huvc 


224 


ASTRONOMY. 


to  have  made  a  very  happy  use  of  this  superstition,  as  already 
stated  on  a  previous  page.     (Art.  433.) 

457.  Eclipses  can  be  calculated  with  the  greatest  precision, 
not  only  for  a  few  years  to  come,  but  for  centuries  and  ages 
either  past  or  to  come.  This  fact  demonstrates  the  truth  of  the 
Copernican  theory,  and  illustrates  the  order  and  stability  that 
everywhere  reign  throughout  the  planetary  regions. 

The  following  is  a  list  of  all  the  solar  eclipses  visible  in  Europe  and  America  from 
1858  to  the  close  of  the  present  century.  To  those  visible  in  New  England,  the  number 
of  digits  is  annexed. 


Year. 

Month. 

Day  and  hour. 

Digits. 

Year. 

Month. 

Day  and  hour. 

Digits. 

1868, 
1669, 

Mar. 
July 

15    6  14  A.  M. 
29    5  32  P.  M. 

1% 
2>$ 

1878, 
1879, 

July 
July 

29    4  56  P.  M. 
19    2    0  A.  M. 

IK 

1860, 

July 

18    7  23  A.  M. 

6H 

1830, 

Dec. 

31    7  30  A.  M. 

5H 

1S61, 

Dec. 

31    7  30  A.  M. 

4^ 

1882, 

May 

17    1    0  A.  M. 

1S63, 

May 

17    1    0  P.  M. 

1885, 

Mar. 

16    0  35  A.  M. 

6* 

1865, 

Oct. 

19    9  10  A.  M. 

3% 

1886, 

Aug. 

29     6  30  A.  M. 

0* 

1866, 

Oct. 

8  11  12  A.  M. 

0 

1887, 

Aug. 

18  10    0  P.  M. 

186T, 

Mar. 

6    8    0  A.  M. 

1890, 

June 

17    8    0  A.  M. 

1868, 

Feb. 

23  10     0  A.  M. 

1891, 

June 

600  Mer. 

1869, 

Aug. 

7    5  21  A.  M. 

lOli 

1892, 

Oct. 

20    0  19  P.  M. 

854 

1870, 

Dec. 

22    6    0  A.  M. 

•   1 

1895, 

Mar. 

26    4    0  A.  M. 

1873, 

May 

26    3    0  A.  M. 

1896, 

Aug. 

900  Mer. 

1874, 

Oct. 

10    4    0  A.  M. 

1897, 

July 

29    9    8  A.  M.  1      4% 

1875, 

Sept. 

29    5  56  A.  M. 

n%   ; 

1899, 

June 

800  Mer. 

1876, 

Mar. 

25    4  11  P.  M. 

3%  ! 

1900, 

May 

28    8    9  A.  M.  1     11 

The  eclipses  of  1869, 1875,  and  1900  will  be  yery  large.  In  those  of  1873, 1875,  and 
18SO,  the  Sun  wili.  rise  eclipsed. 

That  of  1875  will  be  annular.  The  scholar  can  continue  thii  table,  or  extend  it  *vjck- 
war<'<?,-by  adding  or  substracting  the  Chaldean  period  of  18  years,  11  days,  1  hours,  5-i 
minutes,  and  31  seconds. 


CHAPTER  YI. 


PRIMARY    PLANETS    CONTINUED-MARS    AND    THE 
ASTEROIDS. 

458.  MARS  is  the  first  of  the  exterior  planets,  its  orbit  lying 
jmmediately  without,  or  beyond,  that  of  the  Earth,  while  those 
of  Mercury  and  Venus  are  within.  He  appears,  to  the  naked 
eye,  of  a  fine  ruddy  complexion  ;  resembling,  in  color,  and  appa- 

the  ignorant  and  superstitious  regarded  eclipses  ?  457.  What  said  of  the  calculation  of 
eclipses?  What  does  this  demonstrate  and  illustrate?  458.  Position  of  Mars' orbit? 
Row  doeu  he  appoar  to  the  naked  eye?  When  most  brilliant?  When  least? 


THE    PRIMARY    PLANETS MARS    AND    THE    ASTEROIDS.    225 

rent  magnitude,  the  star  Antares,  or  Aldebaran,  near  which  it 
frequently  passes.  It  exhibits  its  greatest  brilliancy  about  the 
time  that  it  rises  when  the  Sun  sets,  and  sets  when  the  Sun 
rises  ;  because  it  is  then  nearest  the  Earth.  It  is  least  brilliant 
when  it  rises  and  sets  with  the  Sun ;  for  then  it  is  five  times  farther 
removed  from  us  than  in  the  former  case. 

459.  Its  distance  from  the  Earth  at  its  nearest  approach  is 
about  50,000,000  of  miles.     Its  greatest  distance  from  us  is 
about  240,000,000  of  miles.     In   the   former  case,  it  appears 
nearly  25  times  larger  than  in  the  latter.     When  it  rises  before 
the  Sun,  it  is  our  morning  star  ;  when  it  sets  after  the  Sun,  it  ia 
our  evening  star. 

The  distance  of  the  interior  planets  from  the  earth,  varies  within  the  limits  of  the 
di.-imeters  of  their  respective  orbits ;  for  when  a  planet  is  in  that  part  of  its  orbit  which 
is  nearest  the  Earth,  it  is  evidently  nearer  by  the  whole  diameter  of  its  orbit,  than  it  is 
when  at  a  point  opposite,  on  the  other  side  of  its  orbit.  The  exterior  planets  vary  in 
distance  within  the  limits  of  the  diameter  of  the  Earth's  orbit. 

460.  Mars  is  sometimes  seen  in  opposition  to  the  Sun,  and 
sometimes  in  superior  conjunction  with  him  ;  sometimes  gibbous, 
but  never  horned.     In  conjunction,  it  is  never  seen  to  pass  over 
the  Sun's  disc,  like  Mercury  and  Venus.     These  prove  not  only 
that  its  orbit  is  exterior  to  the  Earth's  orbit,  but  that  iHs  an 
opaque  body,  shining  only  by  the  reflection  of  the  Sun. 

461.  The  motion  of  Mars  through   the  constellations  of  the 
zodiac  is  but  little  more  than  half  as  great  as  that  of  the  Earth; 
it  being  generally  about  57  days  in  passing  over  one  sign,  which 
is  at  the  rate  of  a  little  more  than  half  a  degree  each  day.  Thus, 
if  we  know  what  constellation  Mars  enters  to-day,  we  may  con- 
clude that  two  months  hence  it  will  be  in  the  next  constellation ; 
four  months  hence,  in  the  next  ;  six  months,  in  the  next,  and 
so  on. 

Its  mean  sidereal  revolution  is  performed  in  686.9796458  solar  days  ;  or  in  686  days,  23 
hours,  30  minutes,  41.4  seconds.  Its  synodical  revolution  is  performed  in  779.936  solar 
days  ;  or  in  779  days,  22  hours,  27  minutes,  and  50  seconds. 

462.  Mars  performs   his  revolution  around  the  Sun  in  one 
year  and  10^  months,  at  the  distance  of  145,000,000  of  miles  ; 
moving  in  its  orbit  at  the  mean  rate  of  55,000  miles  an  hour. 
Its  diurnal  rotation  on  its  axis  is  performed  in  24  hours,  39 


459.  Its  distance  from  the  Earth?  What  effect  upon  its  apparent  magnitude  ?  When 
morning  and  evening  star  ?  How  do  the  distances  of  the  planets  from  the  Earth  vary  \ 
Their  apparent  diameters  ?  460.  Is  Mars  ever  in  opposition  to  the  Sun?  In  conjunc- 
tion? Its  phases?  Does  it  ever  transit  the  Sun?  What  do  these  facts  prove  ?  461. 
What  is  his  rate  of  motion  through  the  constellations  ?  What  calculation  based  upon  it '/ 
462.  His  periodic  time  ?  Distance  from  the  Sun  ?  Mean  rate  of  motion  per  hour?  Time 
o:'  rotation  on  his  axis?  How  does  his  day  compare  with  ours  ? 


226  ASTRONOMY. 

minutes,  and  21£  seconds ;  which  makes  its  day  about  44  min- 
utes longer  than  ours. 

463.  Its   form  is  that  of   an   oblate  spheroid,   whose  polar 
diameter  is  to  its  equatorial,  as  15  is  to  16,  nearly.  Its  diameter 
is  4,500  miles.     Its  bulk,  therefore,  is  7  times  less  than  that  of 
the  Earth  ;  and  being  50,000,000  of  miles  farther  from  the  Sun, 
it  receives  from  him  only  half  as  much  light  and  heat. 

464.  The  inclination  of  its  axis  to  the  plane  of  its  orbit,  is 
about  28f°.     Consequently,  its  seasons  must  be  very  similar  to 
those  of  the  Earth.     Indeed,  the  analogy  between  Mars  and  the 
Earth  is  greater  than  the  analogy  between  the  Earth  and  any 
other  planet  of  the  solar  system.     Their  diurnal  motion,  and  of 
course  the  length  of  their  days  and  nights,  are  nearly  the  same  ; 
the  obliquity  of  their  ecliptics,  on  which  the  seasons  depend,  are 
not  very  different  ;  and,  of  all  the  superior  planets,  the  distance 
of  Mars  from  the  Sun  is  by  far  the  nearest  to  that  of  the  Earth  ; 
nor  is  the  length  of  its  year  greatly  different  from  ours,  when' 
compared  with  the  years  of  Jupiter,  Saturn  and  Uranus. 

465.  To  a  spectator  on  this  planet,  the  Earth  will  appear 
alternately,  as  a  morning  and  evening  star  ;  and  will  exhibit  all 
the  phases  of  the  Moon,  just  as  Mercury  and  Yenus  do  to  us  ; 
and  sometimes  like  them,  will  appear  to  pass  over  the  Sun's  disc 
like  a  dark  round  spot.     Our  Moon  will  never  appear  more  than 
a  quarter  of  a  degree  from  the  Earth,  although  her  distance  from 
it  is  239,000  miles.     If  Mars  be  attended  by  a  satellite,  it  is  too 
small  to  be  seen  by  the  most  powerful  telescopes. 

When  it  is  considered  that  Vesta,  the  smallest,  of  the  asteroids,  which  is  once  and  .* 
half  times  the  distance  of  Mars  from  us,  and  only  269  miles  in  diameter,  is  perceivable 
in  the  cpen  space,  and  that  without  the  presence  of  a  more  conspicuous  body  to  point  it 
out,  we  may  reasonably  conclude  that  Mars  is  without  a  Moon. 

466.  The  progress  of  Mars  in  the  heavens,  and  indeed  of  all 
the  superior  planets,  will,  like  Mercury  and  Yenus,  sometimes 
appear  direct,  sometimes  retrograde,  and  sometimes  he  will  seem 
stationary.     The  portion  of  the  ecliptic  through  which  a  planer 
seems  to  retrograde  is  called  the  Arc  of  Retrogradation.     Thb 
more  remote  the  planet  the  less  the  arc,  and  the  longer  the  time 
of  its  retrogression.     These  retrograde  movements  and  stations, 
as  they  appear  to  a  spectator  from  the  Earth,  are  common  to 
all  the  planets,  and  demonstrate  the  truth  of 'the.  Copernican 
system. 

463.  Form  of  Mars ?  Diameter?  Bulk?  Light  and  heat?  464.  Inclination  of  his 
axis  to  the  plane  of  his  orbit?  His  seasons?  Resemblance  to  our  globe?  465.  How 
would  the  Earth  appear  to  a  spectator  upon  Mars  ?  Our  Moon  ?  Has  Mars  a  satellite  ? 
466.  What  said  of  the  motions  of  Mars  and  the  other  planets?  What  constitutes  *h-_ 


THE  PRIMARY  PLANETS MARS  AND  THE  ASTEROIDS.  227 


RETROGRADE  MOTION   OF  THE   EXTERIOR   PLANETS. 


Suppose  the  Earth  at  A,  and  the  planet  Neptune  at  B,  he  would  then  appear  to  be  at  C, 
among  the  stars ;  but  as  Neptune  moves  but  a  little  from  B  toward  F,  while  the  Earth  h> 
passing  from  A  to  D,  Neptune  will  appear  to  retrograde  from  C  to  E.  Whatever  Neptune 
may  have  moved,  however,  from  B  toward  F,  will  go  to  reduce  the  amount  of  apparent 
retrogression. 

It  is  obvious  from  this  figure-,  that  the  more  distant  an  exterior  planet  is,  and  the  slower 
it  moves,  the  less  will  be  its  arc  of  retrogradation,  and  the  longer  will  it  be  retrograding. 
Neptune  appears  to  retrograde  180  days,  or  nearly  half  the  year. 

The  following  table  exhibits  the  amownt  of  arc  and  the  Ume  of  the  retrogradation  of 
the  principal  planets : 

Arc.  Days. 

Mercury 13%° 23 

Venus  16      42 

Mars  16      73 

Jupiter 10 121 

Saturn 6 139 

Uranus    4      151 

Neptune..  1      180 

TELESCOPIC   APPEARANCES  OF  MARS. 


The  right-hand  figure  represents  Mars  as  seen  at  the  Cincinnati  Observatory,  August  5, 
1845.  On  the  30th  of  the  same  month  he  appeared  as  represented  on  the  left.  lu« 
middle  view  is  from  a  d-awing  by  Dr.  Dick. 

467.  The  telescopic  phenomena  of  Mars  afford  peculiar  interest 
to  astronomers.  They  behold  its  disc  diversified  with  numerous 
irregular  and  variable  spots,  and  ornamented  with  zones  and 
belts  of  varying  brilliancy,  that  form,  and  disappear,  by  turns. 
Zones  of  intense  brightness  are  to  be  seen  in  its  polar  regions, 
subject,  however,  to  gradual  changes.  That  of  the  southern 
pole  is  much  the  most  brilliant.  I)r.  Herschel  supposes  that 
they  are  produced  by  the  reflection  of  the  Sun's  light  from  tho 
frozen  regions,  and  that  the  melting  of  these  masses  of  polar  ice 
is  the  cause  of  the  variation  in  their  magnitude  and  appearance. 


Arc  of  Eftrogradation  f  What  do  these  motion?  prove?        4G7.  How  does  Mars  appear 
through  a  telescope?    Dr.  Herschei'a  opinion  of  its  polar  regions?    H^w  conl-rmeU  iu 

10* 


228  ASTRONOMY. 

He  was  the  more  confirmed  in  these  opinions  by  observing  that  after  the  exposure  of 
the  luminous  zone  about  the  north  pole  to  a  summer  of  eight  months,  it  was  considerably 
decreased,  while  that  on  the  south  pole,  which  had  been  in  total  darkness  during  sight 
mouths,  had  considerably  increased.  He  observed,  farther,  that  when  this  spot  wae 
most  luminous,  the  disc  of  Mars  did  not  appear  exactly  round,  and  that  the  bright  part 
of  its  southern  limb  seemed  to  be  swollen  or  arched  out  beyond  the  proper  curve. 

468.  The  extraordinary  height  and  density  of  the  atmosphere 
of  Mars,  are  supposed  to  be  the  cause  of  the  remarkable  redness 
of  its  light.  It  has  been  found,  by  experiment,  that  when  a 
beam  of  white  light  passes  through  any  colorless  transparent 
medium,  its  color  inclines  to  red,  in  proportion  to  the  density  of 
die  medium,  and  the  space  through  which  it  has  traveled.  Thus 
the  Sun,  Moon,  and  stars,  appear  of  a  reddish  color  when  near 
'the  horizon  ;  and  every  luminous  object,  seen  through  a  mist,  is 
of  a  ruddy  hue. 

This  phenomena  may  be  thus  explained  : — The  momentum  of  the  red,  or  least  refrangi- 
ble rays,  being  greater  than  that  of  the  violet,  or  most  refrangible  rays,  the  former  will 
make  their  way  through  the  resisting  medium,  while  the  latter  are  either  reflected  or 
absorbed.  The  color  of  the  beam,  therefore,  when  it  reaches  the  eye,  must  partake  of 
the  color  of  the  least  refrangible  rays,  and  this  color  must  increase  with  the  distance. 
The  dim  light,  therefore,  by  which  Mars  is  illuminated,  having  to  pass  twice  through  its 
atmosphere  before  it  reaches  the  Earth,  must  be  deprived  of  a  great  proportion  of  its 
violet  rays,  and  consequently  then  be  red.  Dr.  Bru  water  supposes  that  the  difference  of 
color  among  the  other  planets,  and  even  the  fixed  stars,  is  owing  to  the  different  heighta 
and  densities  of  their  atmospheres. 


THE  ASTEROIDS,  OK  TELESCOPIC  PLANETS. 

469.  Ascending  higher  in  the  solar  system,  we  find,  between 
the  orbits  of  Mars  and  Jupiter,  a  cluster  of  eighty-five  small 
planets,  which  present  a  variety  of  anomalies  that  distinguish 
them   from   all  the  older  planets  of  the  system.     The  first  of 
these,  namely,    Ceres,   was    discovered    by   Piazzi,  at  Palermo, 
January  1,  1801;  and  three  others,  namely,  Pallas,  Juno,  and 
Vesta,  have  been  known  since  1807.     The  remaining  eighty-one 

have  all  been  discovered  since  that  time,  and  most  of  them  since 
1853. 

470.  The  scientific  Bode  entertained   the   opinion,  that  the 
planetary  distances,  above  Mercury,  formed  a  geometrical  series, 
3ach  exterior  orbit  being  double  the  distance  of  its  next  interior 
one,  from  the  Sun  ;  a  fact  which  obtains  with  remarkable  exact- 
ness between  Jupiter,  Saturn,  and  Uranus.     But  this  law  seemed 
to  be  interrupted  between  Mars  and  Jupiter.  Hence  he  inferred, 
that  there  was  a  planet  wanting  in  that  interval ;  which  is  now 

this  opi  ion?  468.  Supposed  cause  of  the  ruddy  color  of  Mars?  Philosophical  expla- 
nation *  Dr.  firewater's  opinion  ?  469.  Position  and  numi  ^r  of  the  asteroid*  ?  When 
discover  d?  470.  Bode's  theory?  What  seeming  interruption?  What  conclusioi  ? 


THE  PRIMARY  PLANETS MARS  AND  THE  ASTEROIDS.  2"*J 

happily  supplied  by  the  discovery  of  the  numerous  star-form 
planets,  occupying  the  very  space  where  the  unexplained  vacancy 
presented  a  strong  objection  to  his  theory. 

According  to  Bode,  the  distances  of  the  planets  may  be  expressed  nearly  as  follows :  the 
Earth's  distance  from  the  Sun  being  10. 
Mercury  4 


Venus  4+3x1        =          7 

The  Earth  4  +  3x2        =        10 

Mara  4+3x22       -        16 


Asteroids  4+3x23  =  23 

Jupiter  4+3  x24  =  52 

Saturn  4+3x2°  =  100 

Herschel  4+3x23  =  196 


Comparing  these  values  with  the  actual  mean  distances  of  the  planets  from  the  Sun, 
Tit,  cannot  but  remark  the  near  agreement,  and  can  scarcely  hesitate  to  pronounce  that 
the  respective  distances  of  the  planets  from  the  Sun,  were  assigned  according  to  a  lav, 
although  we  are  entirely  ignorant  of  the  exact  law,  and  of  the  reason  for  that  law.— • 
Brinkley's  Elements,  p.  89. 

411.  The  Asteroids  are  much  smaller  in  size  than  the  older 
planets — they  all  revolve  at  nearly  the  same  distances  from  the 
Sun,  and  perform  their  revolutions  in  nearly  tfie  same  periods — 
their  orbits  are  much  more  eccentric,  and  have  a  much  greater  incli- 
nation to  the  ecliptic — and  what  is  altogether  singular,  except  in 
the  case  of  comets — some  of  their  orbits  cross  each  other  ;  so  that 
there  is  even  a  possibility  that  two  of  these  bodies  may,  some 
time,  in  the  course  of  their  revolutions,  come  into  collision. 

The  orbit  of  Vesta  is  so  eccentric,  that  she  is  sometimes 
farther  from  the  Sun  than  either  Ceres,  Pallas,  or  Juno,  although 
her  mean  distance  is  many  millions  of  miles  less  than  theirs.  The 
orbit  of  Vesta  crosses  the  orbits  of  several  other  asteroids,  in 
two  opposite  points. 

The  student  should  here  refer  to  the  Figures,  Map  I.  of  the  Atlas,  and  verify  such  of 
those  particulars  as  are  there  represented.  It  would  be  well  for  the  teacher  to  require 
him  to  observe  particularly  the  positions  of  their  orbits,  and  to  state  their  different 
degrees  of  inclination  to  the  plane  of  the  ecliptic. 

472.  From  these  and  other  circumstances,  many  eminent 
astronomers  are  of  opinion,  that  these  eighty-five  planets  arc 
the  fragments  of  a  large  celestial  body  which  once  revolved 
between  Mars  and  Jupiter,  and  which  burst  asunder  by  some 
tremendous  convulsion,  or  some  external  violence.  The  dis- 
covery of  Ceres, -by  Piazzi,  on  the  first  day  of  the  present  cen- 
tury, drew  the  attention  of  all  the  astronomers  of  the  age  to 
that  region  of  the  sky,  and  every  inch  of  it  was  minutely  explor- 
ed. The  consequence  was,  that  in  the  year  following,  Dr.  Olbers, 
of  Bremen,  announced  to  the  world  the  discovery  of  Pallas, 
situated  not  many  degrees  fro;>«  Ceres,  and  very  much  resembling 
it  in  size. 


How  substantially  ju^.fied?  471.  Size  of  the  asteroids?  Distance  from  the  Sun? 
Periodic  time?  Forms  of  their  orbits?  Position  with  respect  to  the  ecliptic  '  Wha', 
other  singularity  in  their  orbits  ?  What  remarkable  facts  respecting  the  orbit  01  Vesta  ? 
413.  Whal  conclusion  has  been  drawn  froir  these  facts?  Progress  of  discovery? 


ASTRONOMY. 

473.  From  this  discovery,  Dr.  Olbers  first  conceived  the  idea 
that  these  bodies  might  be  the  fragments  of  a  former  world  ;  and 
if  so,  that  other  portions  of  it  might  be  found  either  in  the  same 
neighborhood,  or  else,  having  diverged  from  the   same   point, 
"  they  ought  to  have  two  common   points  of  reunion,  or  two 
nodes  in  opposite  regions  of  the  heavens  through  which  all  the 
planetary  fragments  must  sooner  or  later  pass," 

474.  One  of  these  nodes  he  found  to  be  in  the  constellation 
Virgo,  and  the  opposite  one  in  the  Whale  ;  and  it  is  a  remark- 
able coincidence  that  it  was  in  the  neighborhood  of  the  latter 
constellation  that  Mr.  Harding  discovered  the  planet  Juno.     In 
order,    therefore,    to   detect   the   remaining   fragments,  if  any 
existed,  Dr.  Olbers  examined,  three  times  every  year,  all  the 
small  stars  in  Virgo  and  the  Whale  ;  and  it  was  actually  in  the 
constellation  Virgo,  that  he  discovered  the  planet  Vesta.    Since 
that  time,  eighty-one  additional  asteroids  have  been  discovered, 
and  it  is  not  unlikely  that  still  additional  fragments  of  a  similar 
description  will  hereafter  be  discovered. 

Dr.  Brewster  attributes  the  fall  of  meteoric  stones  to  the 
smaller  fragments  of  these  bodies  happening  to  come  within  the 
sphere  of  the  Earth's  attraction. 

Meteoric  stones,  or  what  are  generally  termed  aerolites,  are  stones  which  sometimes 
fall  from  the  upper  regions  of  the  atmosphere  upon  the  Earth.  The  substance  of  which 
they  are  composed,  is,  for  the  most  part,  metallic,;  but  the  ore  of  which  it  consists  is  not 
to  be  found  in  the  same  constituent  proportions  in  any  known  substance  upon  the  Earth. 
Their  fall  is  generally  preceded  by  a  luminous  appearance,  a  hissing  noise,  and  a  loud 
explosion ;  and  when  found  immediately  after  their  descent,  they  are  always  hot,  and 
usually  covered  with  a  black  crust,  indicating  a  state  of  exterior  fusion. 

Their  size  varies  from  that  of  small  fragments  of  inconsiderable  weight  to  that  of  the 
most  ponderous  masses.  They  have  been  found  to  weigh  from  300  pounds  to  several  tons  ; 
and  they  have  descended  to  the  earth  with  a  force  sufficient  to  bury  them  many  feet 
under  the  surface. 

Some  have  supposed  that  they  are  projected  from  volcanoes  in  the  Moon  ;  others  that 
they  proceed  from  volcanoes  on  the  Earth ;  while  others  imagine  that  they  are  gene- 
rated in  the  regions  of  the  atmosphere  ;  but  the  truth  probably  is  not  yet.  ascertained,  li 
some  instances,  these  stones  have  penetrated  through  the  roofs  of  houses,  and  proved 
destructive  to  the  inhabitants. 

If  we  carefully  compute  the  force  of  gravity  in  the  Moon,  we  shall  find  that  if  a  body 
were  projected  from  her  surface  with  a  momentum  that  would  cause  it  to  move  at  the  rate 
of  82uO  feet  in  the  first  second  of  time,  and  in  the  direction  of  a  line  joining  the  centers 
of  the  Earth  and  Moon,  it  would  not  fall  again  to  the  surface  of  the  Moon  ;  but  would 
become  a  satellite  to  the  Earth.  Such  an  impulse  might,  indeed,  cause  it,  even  after 
many  revolutions,  to  fall  to  the  earth.  The  fall,  therefore,  of  these  stones,  from  the  air, 
may  be  accounted  for  in  this  manner. 

Mr.  Harte  calculates,  that  even  a  velocity  of  6000  feet  in  a  second,  would  be  sufficient 
to  carry  a  body  projected  from  the  surface  of  the  Moon  beyond  the  power  of  her  attrac- 
tion. If  so,  a  projectile  force  three  times  greater  than  that  of  a  cannon,  would  carry  a 
a  body  from  the  Moon,  beyond  the  point  of  equal  attraction,  and  cause  it  to  reach  the 
Earth.  A  force  equal  to  this  is  often  exerted  by  our  volcanoes,  and  by  subterranean 
steam.  Hence,  there  is  no  impossibility  in  the  supposition  of  their  coming  from  the  Moon. 

473.  Theory  of  Dr.  Olbers  ?  474.  Where  did  he  find  these  nodes?  What  remarkable 
coincidence?  Dr.  Olbers' efforts  ?  Discoveries  since?  Dr.  Brewster's  idea  respecting 
•noteoric  stones  ?  What  are  meteoric  stones?  Circumstances  of  their  fall  ?  Sizis  and 
vciynt?  Supposed  origin  ?  Coul-i  they  have  fallen  fror  the  Moon?  What  computation:;  f 


THE  PRIMARY  PLANETS TABLE  OF  THE  ASTEHOIDS.   23* 

475.  Vesta  appears  like  a  star  of  the  sixth  magnitude,  and  io 
the  only  asteroid  that  can  be  seen  by  the  naked  eye. 

476.  Juno  revolves  around   the  sun  in  4  years  4^-  months. 
Her  diameter  is  estimated  at  1,393  miles.     She  is  noted  for  the 
great  eccentricity  of  her  orbit.     Ceres'  diameter  is  estimated  at 
1,585  miles,  and  Pallas'  at  2,025. 


TABLE   OF  THE  ASTEROIDS. 

477.  The  following  table  comprises  the  names,  distances, 
periods,  etc.,  of  the  Asteroids,  so  far  as  known.  They  are 
placed  in  the  order  of  their  discovery. 


No.        Names. 

Distance  from 
the  Sun  in 
Miles. 

Periodic 
time   in 
Days. 

time  of 
discovery. 

By  whom 
discovered; 

Wh?re 
discnve  a 

1.  Ceres  
2.  Pallas  

262,764,110 
263,186,670 
253.524,410 
224,327,205 
244.767,500 
230,414,710 
22<5,  683.965 
209,131,670 
226,644.350 
299,190,435 
232,995,860 
221,617.045 
244,684,375 
245,989,960 
251,197,100 
277,661,440 
235.002,450 
218,125,700 
231,929,960 
228,891,670 
231,365.945 
237,080,005 
249,738.280 
299.244,965 
228,100,700 
252,327,505 
222,993,975 
263,641,815 
242,712,270 
224,598,905 
299,835,010 
245.958,705 
272,372,125 
255,388,690 

1,680 
1,684 
1,592 
1,325 
1,511 
1,380 
1,346 
1,193 
1,346 
2.041 
1,403 
1,301 
1,510 
1,522 
1,570 
1,825 
1,421 
1,271 
1,393 
1,366 
1,388 
1,440 
1,557 
2,042 
1,859 
1,581 
1,314 
1,689 
1,492 
1,328 
2,048 
1,522 
1,773 
1,610 

Jan.        1.  1801 
March  28,  1802 
Sept.      1,  1804 
March  29,  1807 
Dec.       8,  1845 
July      1,  1847 
Aug.    13.  1847 
Get      18,  1847 
April   25,1848 
April    12,1849 
May     13,  1850 
Sept    13,1850 
Nov.      2,  1850 
May     20,  1851 
July     29,  1851 
March  17,  1852 
April    17,1852 
June    24,1852 
Aug.     22,  1852 
Sept    19,1852 
Nov.    15,  1852 
Nov.    16,  1852 
Dec.     15,  1852 
April      5,  1853 
April     6,  1853 
May       5,  1853 
Nov.      8.  1853 
March    1,  1854 
March    1,  1854 
July     22,  1854 
Sept.      1,  1854 
Oct      26,  1854 
Oct      28,  1854 
April    15,  1855 

Piazzi  
Dr.  Olbers 
Harding.. 
Dr.  Olbers 
Hencke.. 
Hencke. 
Hind.... 
Hind.  .  .  . 
Graham  . 
De  Gasparis 
De  Gasparis 
Hind  
De  Gasparis 
Hind 

Palermo. 
Bremen. 
Lilienthal. 
Bremen. 
Drh'sden. 
Driesden. 
London. 
London. 
Markvee. 
Naples. 
Naples. 
London. 
Naples. 
London. 
Naples. 
Naples. 
Bilk. 
London. 
London. 
Marseilles. 
Paris. 
London. 
London. 
Naples. 
Marseilles 
Bilk. 
London. 
Bilk. 
London. 
London. 
Washington,  D.  CL 
Paris. 
Paris. 
Paris. 

8   Juno.       .   .  . 

4.  Vesta  
5.  Astrsea.  
6.  Hebe  

7   Iris. 

8.  Flora  
9.  Metis  
10.  Hyeeia  
11.  Parthenope  . 
12    Clio 

13.  Egeria  
14.  Irene    
15.  Ennomia  .  .  . 
16.  Psyche  
17.  Thetis  
18.  Melpomena 
19.  Fortuna  
20.  Massilia  .... 
21.  Lutetia  
22.  Calliope  
23.  Thalia  
24.  Themis  
25.  Phoctea  
26.  Proserpine.. 
27.  Euterpe  
28.  Bellona.... 
29.  Amphitrite  . 
80.  Urania  
81.  Euphrosyne 
82.  Pomona  
83.  Polymnia... 
84.  Circe  

De  Gasparis 
De  Gasparis 
Luther  
Hind  
Hind  
Chacornac.. 
Goldsmidt.. 
Hind  
Hind     . 

De  Gasparis 
Chacomac  .  . 
Luther    
Hind... 
Luther  
Marth  
Hind  
Ferguson  .. 
Goldsmidt 
Chacornac.  . 
Chacornac.. 

475.  Appearance  of  Vesta.    476.  Juno's  period.    Diameter.    For  ^hat  noted  ?     Di 
meter  of  Ceres.    Of  Pallas.    477.  Numbei  of  asteroids  now  kno^vn  a*  per  tabl« 


232  ASTBOXOHY 

TA3LE   OF  THE  ASTEROIDS.—  Continued. 


No.  Names. 

Distance  from 
the  Sun   in 
Mil^B. 

Periodic 
time   in 
Days. 

T'me  of 
discovery. 

By  whim 
discovered. 

Wh^re 
discovert  d. 

86.  Leucothea  .  . 
86.  Atalanta.... 
87   Fides 

288,216,755 
261.126,975 
255,981,165 
260.270,075 
263,091,765 
215,379,060 
228.032,015 
231,219,455 
209,364,610 
230,886,670 
260,568.660 
241.296.960 
273,641,325 
295.150,275 
293,180,925 
251vS44,430 
225,901,640 
294,330,710 
248,224,930 
258,811,540 
263,965,195 
245,428,700 
299,942.265 
255,971,895 
257.714,955 
227,203,995 
285.377,815 
297.430,750 
221654,200 
254.437,170 
325;996,965 
252,117,278 
229,421,200 
258.652.510 
290,924,010 
253.662,065 
208,788,740 
261,841,470 
254.435,102 
244.645.135 
261,121,806 
302,955,000 
253,521,413 
262,418,500 
232.294,000 
215.390,742 
263,981,794 
257,814,930 
232,297,428 
225,900,271 
252,117,294 

1,880 
1,665 
1,568 
1,656 
1,683 
1,247 
1,358 
1,887 
1,195 
1.384 
L659 
1,479 
1.786 
2,000 
1.980 
1,577 
1.839 
1,992 
1,543 
1,642 
1,692 
1,517 
2,049 
1,615 
1,632 
1,351 
1,902 
2,024 
1,355 
1,601 
2,322 
1,579 
1,371 
1,641 
1,957 
1,594 
1,148 
1,671 
1,589 
1,509 
1,570 
2,080 
1,597 
1,677 
1,397 
1,271 
1,693 
1.659 
1.382 
1,824 
1,572 

April  19,1855 
Oct.       5,  1855 
Oct.        5,  1855 
Jan.      12,  1856 
Feb.       8,  1856 
March  81,  1856 
May     23,  1856 
May     23,  1856 
April    15,  1857 
May     27,  1857 
June    27,  1S57 
Aug.    16,  1857 
Sept.    15,  1857 
Sept.    19,1857 
Sept.    19,  1857 
Oct.       4,  1857 
Jan.     22,  1858 
Feb.       4,  1858 
April     4,  1858 
Sept.    11,  1858 
Sept.    11,1858 
Sept.      9,  1859 
Sept.    22,1859 
March  24,  1860 
Sept.     12,  1860 
Sept.    15,  1860 
Sept.    19,1860 
Oct.      10,  1860 
Feb.     10.  1861 
March    2,1861 
March   4,  1861 
April     9,  1861 
April    17,1861 
April    20,1861 
April    29,1861 
May       5,  1861 
May     29,  1861 
Aug.    18,  1861 
April     7,  1862 
Aug.    29,  1862 
Sept.    22,1862 
Oct.      21,  1862 
Nov.    12,  1862 
March  15,  1863 
Sept.    14,  1S63 
May       2,  1864 
Sept.    30,1864 
Nov.    27,1864 
April  26,  1865 
Ang     25,  1865 
Sept.    19,  1865 

Luther  
Goldsmidt.. 
Luther  
Chacornac.. 
Chacornac.. 
Goldsmidt.. 
Goldsmidt.. 
Pogson  
Pogso-n  .   ... 
Goldsmidt.. 
Goldsmidt.  . 
Pogson  
Luther  
Goldsmidt.. 
Goldsmidt.  . 
Ferguson  .  .  . 
Laurent  
Goldsmidt.. 
Luther  
Goldsmidt.. 
Searle  
Goldsmidt.. 
Luther  
Luther  .... 
Chacornac.. 
Ferguson... 
Goldsmidt.  . 
Foster   
De  Gasparis 
Tempel  
Tempel  
Tuttle  
Payson  
Luther  
Schiaparelli 
Goldsmidt. 
Peters 

Bilk. 
Paris. 
Bilk. 
Paris. 
Paris. 
Paris. 
?aris. 
Oxford. 
Oxford. 
Paris. 
Paris. 
Oxford. 
Bilk. 
Paris. 
Paris. 
Washington,  D.  C. 
STismes. 
Paris. 
Bilk. 
Paris. 
Albany,  N.  Y. 
Paris. 
Bilk. 
Bilk. 
Paris. 
Washington,  D.  0 
Paris. 
Berlin. 
Naples. 
Marseilles. 
Marseilles. 
Cambridge,  Mass. 
Madras. 
Bilk. 
Milan. 
Paris. 
Clinton,  N.  Y. 
Bilk. 
Cambridge,  Mass. 
Marseilles. 
Clinton,  N.  Y. 
Copenhagen 
Clinton,  N.  Y. 
Bilk. 
Ann  Arbor,  Mich. 
Oxford. 
Marseilles. 
Bilk. 
Naples. 
Bilk. 
Clinton,  N.  Y. 

88  Leda  

89.  Laetitia  
40.  Harmonia  .  . 
41.  Daphne  
42.  Isis  
43.  Ariadue  
44  Nvsa 

45.  Eugenia  
46.  Hestia  
47.  Aglaia  

48.  Doris  
49.  Pales  
50.  Virginia  .... 
51.  Nemausa  
52.  Enropa  
53.  Calypso  
54.  Alexandra  .  . 
55.  Pandora  ... 
56.  Melete  
57.  Mnemosyne 
58.  Concordia  .  . 
59.  Olympia  
60.  Echo  

61  Danae 

62.  Erato  

63.  Ansonia  
64.  Angelina  ... 
65.  Cybele  
66   Maja 

67.  Aria  

68.  Leto  
69.  Hesperia  
70.  Panoptea  
71.  Feronia.... 
72.  Niobe  ...... 
73.  Clytie  
74.  Galatea  
75.  Euiidice.... 
76.  Freia  
77.  Frigga  
78.  Diana  
79.  Eurynome. 
80.  Snppho.  ... 
81.  Terpsichore 
B2.  Alcmene  .. 
83.  Beatrix.., 
84.  Clio... 
85   lo  

Luther.  
Tuttle  
Tempel  
Peters  
M.  D.  Arvert 
Peters  
Luther  
Watson  
Pogson  
Tempel  
Luther  
De  Gasparis 
Luther  .... 
Peters  

THE    PRIMARY    PLANETS— JUPITER    AND    SATURN.       2H3 

CHAPTER  VII. 

PRIMARY  PLANETS— JUPITER   AND  SATURN. 

473.  JUPITER  is  the  largest  of  all  the  planets  belonging  to  the 
eolar  system.  It  may  be  readily  distinguished  from  the  fixed 
stars,  by  its  peculiar  splendor  and  magnitude  ;  appearing  to  the 
naked  eye  almost  as  resplendent  as  Yenus,  although  it  is  more 
than  seven  times  her  distance  from  the  Sun. 

When  his  right  ascension  is  less  than  that  of  the  Sun,  he  is 
our  morning  star,  and  appears  in  the  eastern  hemisphere  before 
the  Sun  rises  ;  when  greater,  he  is  our  evening  star,  and  lingers 
in  the  western  hemisphere  after  the  Sun  sets. 

Nothing  can  be  easier  than  to  trace  Jupiter  among  the  con- 
stellations of  the  zodiac  ;  for  in  whatever  constellation  he  is  seen 
to-day,  one  year  hence  he  will  be  seen  equally  advanced  in  the 
next  constellation  ;  two  years  hence,  in  the  next  ;  three  years 
hence,  in  the  next,  and  so  on  ;  being  just  a  year,  at  a  mean  rate, 
in  passing  over  one  constellation. 

The  exact  mean  motion  of  Jupiter  in  its  orbit,  is  about  one-twelfth  of  a  degree  in  a  day  j 
%'hich  amounts  to  only  80°  20'  32"  in  a  year. 

For  12  years  to  come,  he  will,  at  a  mean  rate,  pass  through 
the  constellations  of  the  zodiac,  as  follows  : 


1867,  Capricornus. 
1863,  Aquarius. 

1869,  Pisces. 

1870,  Aries. 


1871,  Taurus. 

1872,  Gemini. 

1873,  Cancer. 

1874,  Leo. 


1875,  Virgo. 

1876,  Libra. 

1877,  Scorpio. 

1878,  Sagittarius. 


479.  Jupiter  is  the  next  planet  in  the  solar  system  above  the 
asteroids,  and  performs  his  annual  revolution  around  the  Sun  in 
nearly  12  of  our  years,  at  the  mean  distance  of  495,000,000  of 
miles  ;  moving  in  his  orbit  at  the  rate  of  30,000  miles  an  hour. 

The  exact  period  of  Jupiter's  sidereal  revolution  is  11  years,  10  months,  17  days,  14 
hours,  21  minutes,  25%  seconds.  His  exact  mean  distance  from  the  Sun  is  495,533,837 
miles ;  consequently,  the  exact  rate  of  his  motion  in  his  orbit,  is  29,943  miles  per  hour 

480.  He  revolves  on  an  axis,  which  is  nearly  perpendicular  to 
the  plane  of  his  orbit,  in  9  hours,  55  minutes,  and  50  seconds  ; 
so  that  his  year  contains  10,471  days  and  nights  ;  each  about 
5  hours  long. 

His  form  is  that  of  an  oblate  spheroid,  whose  polar  diameter 

478.  Comparative  size  of  Jupiter  ?  How  distinguished  from  the  fixed  stars?  When 
morning  star,  &c.  ?  Is  he  easily  traced  ?  479.  His  position  in  the  system?  His  peri- 
odic time?  Distance  from  the  Sun ?  Rate  of  motion?  480.  Time  of  diurna.  revolu- 
tion? Pa-jition  of  axis?  Length  of  his  days?  Number  in  his  year  ?  His  form  Cau9<f» 
rf  His  obJateness  ?  Difference  of  equatorial  and  polar  diameters  ?  The  Earth  ? 


234  ASTRONOMY. 

is  to  its  equatorial,  as  16  to  IV.  He  is  therefore  considerably 
more  flattened  at  the  poles  than  any  of  the  other  planets,  except 
Saturn.  This  is  caused  by  his  rapid  rotation  on  his  axis  ;  for  it 
is  an  universal  law  that  the  equatorial  parts  of  every  body, 
revolving  on  an  axis,  will  be  swollen  out,  in  proportion  to  the 
density  of  the  body,  and  the  rapidity  of  its  motion. 

The  difference  between  the  polar  and  equatorial  diameters  of  Jupiter,  exceeds  6000 
miles.  The  difference  between  the  polar  and  equatorial  diameters  of  the  Earth,  is  only 
26  miles.  Jupiter,  even  on  the  most  careless  view  through  a  good  telescope,  appears  to 
be  oval ;  the  longer  diameter  being  parallel  to  the  direction  of  his  belts,  which  are  also 
parallel  to  the  ecliptic. 

481.  By  this  rapid  whirl  on  its  axis,  his  equatorial  inhabitants 
are  carried  around  at  the  rate  of  26,554  miles  an  hour  ;  which 
is  1600  miles  farther  than  the  equatorial  inhabitants  of  the 
Earth  are  carried,  by  its  diurnal  motion,  in  twenty-four  hours. 

The  true  mean  diameter  of  Jupiter  is  88,780  miles  ;  which 
is  nearly  11  times  greater  than  the  Earth's.  His  volume  is, 
therefore,  about  thirteen  hundred  times  larger  than  that  of  thr> 
Earth.  ( For  magnitude  as  compa?'ed  with  that  of  the  Earth,  set 
Map  I.)  On  account  of  his  great  distance  from  the  Sun,  the 
degree  of  light  and  heat  which  he  receives  from  it  is  27  times 
less  than  that  received  by  the  Earth. 

;  When  Jupiter  is  in  conjunction,  he  rises,  sets,  and  comes  to  the  meridian  wit*  the  Sun ; 
but  is  never  observed  to  make  a  transit,  or  pass  over  the  Sun's  disc  ;  when  in  opposition, 
he  rises  when  the  Sun  sets,  sets  when  the  Sun  rises,  and  comes  to.  the  meridian  at  mid- 
night, which  never  happens  in  the  case  of  an  interior  planet.  This  proves  that  Jupiter 
revolves  in  an  orbit  which  is  exterior  to  that  of  the  Earth. 

482.  As  the  variety  in  the  seasons  of  a  planet,  and  in  the 
length  of  its  days  and  nights,  depends  upon  the  inclination  of  its 
axis  to  the  plane  of  its  orbit,  and  as  the  axis  of  Jupiter  has 
little  or  no  inclination,  there  can  be  no  difference  in  his  seasons, 
on  the  same  parallels  of  latitude,  nor  any  variation  in  the  length 
of  his  days  and  nights.     It  is  not  to  be  understood,  however, 
that  one  uniform  season  prevails  from  his  equator  to  his  poles  ; 
but  that  the  same  parallds  of  latitude  on  each  side  of  his  equa- 
tor, uniformly  enjoy  the  same  season,  whatever  season  it  may  be. 

About  his  equatorial  regions  there  is  perpetual  summer ;  and 
at  his  poles  everlasting  winter  ;  but  yet  equal  day  and  equal 
night  at  each.  This  arrangement  seems  to  have  been  kindly 
ordered  by  the  beneficent  Creator  ;  for  had  his  axis  been  inclined 
to  his  orbit,  like  that  of  the  Earth,  his  polar  winters  would  have 
been  alternately  a  dreadful  night  of  six  years'  darkness. 

481.  Motion  at  Jupiter's  equator?  His  mean  diameter?  His  volume?  Li^ht  and  heatr 
Does  he  ever  transit  the  Sun?  What  proof  that  his  orbit  is  exterior  to  that  of  tli ;  Earth? 
482.  What  of  the  seasons  of  Jupiter  ?  What  apparent  manifestation  of  Divine  Wisdom? 


THE    PRIMARY    PLANETS JUPITER    AND    SATURN.       235 


TELESCOPIC    VIEW    OF     JUPITKK. 

483.  Jupiter,  when 
viewed     through     a 
telescope,  appears  to 
be  surrounded  by  a 
number  of  luminous 
zones,  usually  termed 
Idls,  tnat  frequently 
extend  quite  around 
him.    These  belts  are 
parallel  not  only  to 
each   other,  but,  in 
general,  to  his  equa- 
tor,   which    is    also 
nearly  parallel  to  the 
ecliptic.       They  are 

subject,  however,  to  considerable  variation,  both  in  breath  and 
number.  Sometimes  eight  have  been  seen  at  once  ;  sometimes  only 
one,  but  more  usually  three.  Dr.  Herschel  once  perceived  his 
whole  disc  covered  with  small  belts,  though  they  are  more 
usually  confined  to  within  30°  of  his  equator,  that  is,  to  a  zone 
60°  in  width. 

Sometimes  these  belts  continue  for  months  at  a  time  with  little 
or  no  variation,  and  sometimes  a  new  belt  has  been  seen  to  form 
in  a  few  hours.  Sometimes  they  are  interrupted  in  their  length  ; 
and  at  other  times,  they  appear  to  spread  in  width,  and  run  into 
each  other,  until  their  breadth  exceeds  5000  miles. 

484.  Bright  and  dark  spots  are  also  frequently  to  be  seen  in 
the  belts,  which  usually  disappear  with  the  belts  themselves, 
though  not  always,  for  Cassini  observed  that  one  occupied  the 
same  position  more  than  40  years.     Of  the  cause,  of  these  vari- 
able appearances,  but  little  is  known.     They  are  generally  sup- 
posed to  be  nothing  more  than  atmospherical  phenomena,  resulting 
from,  or  combined  with,  the  rapid  motion  of  the  planet  upon  its 
axis. 

Different  opinions  have  been  entertained  by  astronomers  respecting  the  cause  of  these 
belts  and  spots.  By  some  they  have  been  regarded  as  clouds,  or  as  openings  in  the 
atmosphere  of  the  planet,  while  others  imagine  that  they  are  of  a  more  permanent 
nature,  and  are  the  marks  of  great  physical  revolutions,  which  are  perpetually  agitating 
and  changing  the  surface  of  the  planet.  The  first  of  these  opinions  sufficiently  explains 
the  variations  in  the  form  and  magnitude  of  the  spots,  and  the  parallelism  of  the  belts. 

483.  How  does  Jupiter  appear  through  a  telescope?  Where  are  his  belts  usually 
•een?  Their  number?  Are  they  permanent?  484.  What  else  seen  upon  Jupiter's 
surface?  Are  they  permanent?  Is  the  cause  of  these  phenomena  well  understood! 
What  different  opinions? 


236 


ASTRONOMY. 


JPhe  spot  first  observed  by  Cassini,  in  1665,  which  has  both  disappeared  and  reappeared 
in  the  &arue  form  and  position  for  the  space  of  43  years,  could  not  possibly  be  occasioned 
by  any  a'imospherical  variations,  but  seems  evidently  to  be  connected  with  the  surface 
»f  th*  plauet.  The  form  of  the  belt,  according  to  some  astronomers,  may  be  accounted 
Tor  by  supposing  that  the  atmosphere  reflects  more  light  than  the  body  of  the  planet, 
und  that  the  clouds  which  float  in  it,  being  thrown  into  parallel  strata  by  the  rapidity  of 
,'ts  diurnal  motion,  form  regular  insterstices,  through  which  are  seen  its  opaque  body,  or 
any  of  the  permanent  spots  which  may  come  within  the  range  of  the  opening. 


TELESCOPIC  VIEWS    OF    THE   MOONS    OF 
JUPITER.    ' 


MOONS  OF  JUPITER. 

485.  Jupiter  is  attended  by  four  satellites  or  moons 
Ai'e  easily  seen  with  a  common  spy- 
glass,  appearing   like    small   stars 

near  the  primary.  (See  adjoining 
cut.)  By  watching  them  for  a  few 
evenings,  they  will  be  seen  to  change 
their  places,  and  to  occupy  different 
positions.  At  times,  only  one  or  two 
may  be  seen,  as  the  others  are 
either  between  the  observer  and  the 
planet,  or  beyond  the  primary,  or 
eclipsed  by  his  shadow. 

486.  The  size  of  these  satellites 
is  about  the  same   as   our   moon, 
except  the  second,  which  is  a  trifle 
less.  The  first  is  about  the  distance 
of  our  moon  ;  and  the  others,  re- 
spectively, about  two,  tbree,  and 
five  times  as  far  off. 


They 


COMPARATIVE  DIST 


4th. 


3d. 


OF  JUPITER'S  MOONS 
2d.         1st. 


487  Their  periods  of  revolution  are  from  1  day  18  hours  to 
17  days,  according  to  their  distances.  This  rapid  motion  is 
necessary,  in  order  to  counterbalance  the  powerful  centripetal 
force  of  the  planet,  and  to  keep  the  satellites  from  falling  to  his 
surface. 


485.  How  many  moons  has  Jupiter ?     How  seen?    Why  not  all  seen  at  once?        436 
their  size?     Distances?        487.  Periods  of  Jupiter's  satellites?    Why  so  rapid? 


THE    PRIMARY    PLANETS JUPITER    AND    SATURN.       287 

The  magnitudes,  distances,  and  periods  of  the  moons  of  Jupiter  are  as  follows: 

Diameter  in  miles.  Distance.  Periodic  times. 

1st 2,500 280,000 1  day  19  hours. 

2d   ..  ...2,200 440,000 8    "    12    " 

8d  3,500 700,000 7    "    14    " 

4th 2,890 1,200,000 6    "    16    " 

488.  The  orbits  of  Jupiter's  moons  are  all  in  or  near  the  plane 
of  his  equator  ;  and  as  his  orbit  nearly  coincides  with  the  eclip- 
tic, and  his  equator  with  his  orbit,  it  follows  that,  like  our  own 
moon,  his  satellites  revolve  near  the  plane  of  the  ecliptic.     On 
this  account,  they  are  sometimes  between  us  and  the  planet,  and 
sometimes  beyond  him,  and  seem  to  oscillate,  like  a  pendulum, 
from  their  greatest  elongation  on  one  side  to  their  greatest  elon- 
gation on  the  other. 

489.  Their  direction  is  from  west  to  east,  or  in  the  direction 
their  primary  revolves,  both  upon  his  axis  and  in  his  orbit.  From 
the  fact  that  their  elongations  east  and  west  of  Jupiter  are  nearly 
the  same  at  every  revolution,  it  is  concluded  that  their  orbits 
are  but  slightly  elliptical.     They  are  supposed  to  revolve  on 
their  respective  axis,  like  our  own  satellite,  the  moon,  once  dur- 
ing every  periodic  revolution. 

490.  As  these  orbits  lie  near  the  plane  of  the  ecliptic,  they 
have  to  pass  through  his  broad  shadow  when  in  opposition  to  the 
Sun,  and  be  totally  eclipsed  at  every  revolution.     To  this  there 
is  but  one  exception.     As  the  fourth  satellite  departs  about  3° 
from  the  plane  of  Jupiter's  orbit,  and  is  quite  distant,  it  some- 
times passes  above  or  below  the  shadow,  and  escapes  eclipse.  But 
such  escapes  are  not  frequent. 

These  moons  are  not  only  often  eclipsed,  but  they  often  eclipse 
Jupiter,  by  throwing  their  own  dark  shadows  upon  his  disc. 
They  may  be  seen  like  dark  round  spots  traversing  it  from  side 
to  side,  causing,  wherever  that  shadow  falls,  an  eclipse  of  the 
Sun.  Altogether,  about  forty  of  these  eclipses  occur  in  the  sys- 
tem of  Jupiter  every  month. 

491.  The  immersions  and  emersions  of  Jupiter's  moons  have 
reference    to   the   phenomena   of    their   being   eclipsed.     Their 
entrance,  into  the  shadow  is  the  immersion  ;   and  their  coming  out 
of  it  the  emersion. 

488.  How  are  their  orbits  situated  ?  How  satellites  appear  to  move  ?  489.  Direction 
ot  secondaries?  Form  of  orbits?  How  ascertained?  What  motion  on  axis?  4i)0. 
What  said  of  eclipses  ?  Of  fourth  satellite  ?  Of  solar  eclipses  upon  Jupiter  ?  Numoer 
of  solar  and  lunar?  491.  What  are  the  immersions  and  emersions  of  Jupiter's 
noons?  Are  the  immersions  and  emersions  always  visible  from  the  Earth?  Why  not? 
UJuatrate. 


238  ASTRONOMY. 

ECLIPSES  3P  JUPITER'S  BOONS,  EMERSIONS,   ETC. 


.'  .-^«3=~-— ',    • 

f/2z&\ 

lj{  i 


The  above  is  a  perpendicular  view  of  the  orbits  of  Jupiter's  satellites.  His  oroad 
shadow  is  projected  in  a  direction  opposite  the  Sun.  At  C,  the  second  satellite  is  suffer- 
ing an  immersion,  and  will  soon  be  totally  eclipsed ;  while  at  D,  the  first  is  in  the  act  of 
emersion,  and  will  soon  appear  with  its  wonted  brightness.  The  other  satellites  are  seen 
to  cast  their  shadows  off  into  space,  and  are  ready  in  turn  to  eclipse  the  Sun,  or  cut  off  a 
portion  of  his  beams  from  the  face  of  the  primary. 

If  the  Earth  were  at  A  in  the  cut,  the  immersion,  represented  at  C,  would  be  invisible  ; 
and  if  at  B,  the  emersion  at  D  could  not  be  seen.  So,  also,  if  the  Earth  were  exactly  at 
F,  neither  could  be  seen  ;  as  Jupiter  and  all  his  attendants  would  be  directly  beyond  the 
Sun,  and  would  be  hid  from  our  view. 

492.  The  system  of  Jupiter  may  be  regarded  as  a  miniature 
representation  of  the  solar  system,  and  as  furnishing  triumphant 
evidence  of  the  truth  of  the  Copernican  theory.  It  may  also  be 
regarded  as  a  great  natural  clock,  keeping  absolute  time  for  the 
whole  world  ;  as  the  immersions  and  emersions  of  his  satellites 
furnish  a  uniform  standard,  and,  like  a  vast  chronometer  hung 
up  in  the  heavens,  enable  the  mariner  to  determine  his  longitude 
upon  the  trackless  deep. 

By  long  and  careful  observations  upon  these  satellites,  astronomers  have  been  able  to 
construct  tables,  showing  the  exact  time  when  each  immersion  and  emersion  will  take 
place,  at  Greenwich  Observatory,  near  London.  Now  suppose  the  tables  fixed  the  time 
for  a  certain  satellite  to  be  eclipsed  at  12  o'clock  at  Greenwich,  but  we  find  it  to  occur  at 
t)  o'clock,  for  instance,  by  our  local  time  :  this  would  show  that  our  time  was  three  hours 
behind  the  time  at  Greenwich  ;  or,  in  other  words,  that  we  were  three  hours,  or  45°,  west 
of  Greenwich.  If  our  time  was  ahead  of  Greenwich  time,  it  would  show  that  we  were 
eaut  of  that  meridian,  to  the  amount  of  15°  for  every  hour  of  variation.  But  this  method 
of  finding  the  longitude  is  less  used  than  the  "lunar  method"  (Art.  407),  on  account  of 
the  greater  difficulty  of  making  the  necessary  observations. 

403.  By  observations  upon  the  eclipses  of  Jupiter's  moons,  as 
compared  with  the  tables  fixing  the  time  of  their  occurrence,  it 
was  discovered  that  light  had  a  progressive  motion,  at  the  rate 
of  about  200,000  miles  per  second. 

This  discovery  may  be  illustrated  by  again  referring  to  the  preceding  cut.  In  the  year 
1675,  it  was  observed  by  Roemer,  a  Danish  astronomer,  that  when  the  Earth  was  nearest 
to  Jupiter,  as  at  E,  the  eclipses  of  his  satellites  took  place  8  minutes  13  seconds  sooner 
than  the  mean  time  of  the  tables ;  but  when  the  earth  was  farthest  from  Jupiter,  as  at 
F,  the  eclipses  took  place  8  minutes  and  13  seconds  laUr  than  the  tables  predicted,  th? 
entire  difference  being  16  minutes  and  26  seconds.  This  difference  of  time  he  ascribed  to 
the  progressive  motion  of  light,  which  he  concluded  required  16  minutes  and  26  seconda 
to  oross  the  earth's  orbit  from  E  to  F. 

492.  How  may  the  system  of  Jupiter  be  regarded  ?    What  use  of  it  made  in  navigation  ? 
Illustrate  method?    Is  it  much  used  ?        493.  What  discovery  by  observing 
of  Jupiter's  moons?    Explain  theorocess? 


THE  PRIMARY  PLANETS JUPITER  AND  SATURN.   "39 

Tins  progress  may  be  demonstrated  as  follows : — 16m.  26s.=9S6s.  If  the  radius  of  tfco 
Earth's  orbit  be  95,000,000  of  miles,  the  diameter  must  be  twice  that,  or  190,000,000. 
Divide  190,000,000  miles  by  986  seconds,  and  we  have  192,697|^|-  miles  as  the  progress 
of  light  in  each  second.  At  this  rate,  light  would  pass  nearly  eight  times  around  the  $;lobc 
at  every  tick  of  the  clock,  or  nearly  500  times  every  minute  ! 

494.  Jupiter,  when  seen  from  his  nearest  satellite,  appears  a 
thousand  times  larger  than  our  Moon  does  to  us,  exhibiting  on  a 
scale  of  inconceivable  magnificence,  the  varying  forms  of  a  cres- 
cent, a  half  moon,  a  gibbous  phase,  and  a  fall  moon,  every  42 
hours. 

SATUKN. 

495.  SATURN  is  situated  between  the  orbits  of  Jupiter  and 
Uranus,  and  is  distinctly  visible  to  the  naked  eye.     It  may  be 
easily  distinguished  from  the  fixed  stars  by  its  pale,  feeble,  and 
steady  light.     It  resembles  the  star  Fomalhaut,  both  in  color 
and  size,  differing  from  it  only  in  the  steadiness  and  uniformity 
of  its  light. 

From  the  slowness  of  its  motion  in  its  orbit,  the  pupil  throughout  the  period  of  hie 
whole  life,  may  trace  its  apparent  course  among  the  stars,  without  any  danger  of  mis- 
take. Having  once  found  when  it  enters  a  particular  constellation,  he  may  easily  remem- 
ber where  he  is  to  look  for  it  in  any  subsequent  year;  because,  at  a  mean  rate,  it  is  just 
2}£  years  in  passing  over  a  single  sign  or  constellation. 

Saturn's  mean  daily  motion  among  the  stars  is  only  about  2', 
the  thirtieth  part  of  a  degree. 

496.  The  mean  distance  of  Saturn  from  the  Sun  is  nearly 
double  that  of  Jupiter,  being  about  909,000,000  of  miles.     His 
diameter  is  about  73,484  miles  ;  his  volume,  therefore,  is  eleven 
hundred  times  greater  than  the  Earth's.     Moving  in  his  orbit  at 
tho  rate  of  22,000  miles  an  hour,  he  requires  29^-  years  to  com- 
plete his  circuit  around  the  Sun  :  but  Ms  diurnal  rotation  on  his 
axis  is  accomplished  in  10J  hours.     His  year,  therefore,  is  nearly 
thirty  times  as  long  as  ours,  while  his  day  is  shorter  by  more 
than  one-half.     His  year  contains  about  25,150  of  its  own  days, 
which  are  equal  to  10,759  of  our  days. 

497.  The  surface  of  Saturn,  like  that  of  Jupiter,  is  diversified 
with  belts  and  dark  spots.     Dr.  Herschel  sometimes  perceived 
five  belts  on  his  surface  ;  three  of  which  were  dark  and  two 
bright.     The  dark  belts  have  a  yellowish  tinge,  and  generally 
cover  a  broader  zone  of  the  planet  than  those  of  Jupiter. 

To  the  inhabitants  of  Saturn,  the  Sun  appears  90  times  less  than  he  appears  at  the 
Earth ;  and  they  receive  from  him  only  one  ninetieth  part  as  much  light  and  heat.  But 

494.  How  does  Jupiter  appear  from  his  nearest  satellite  ?  495.  Situation  of  Saturn  ? 
flow  distinguished?  How  trac-?  His  rate  of  motion  in  the  heavens?  49G.  Distance 
•rom  th«:  Sun?  Diameter?  Volume?  Rate  of  motion  in  orbit  ?  Periodic  time?  Diur 
nal  revolution?  Days  in  his  year?  497.  Appearance  of  his  surface?  Belts  1  The 
seen  from  Stitnrn*  Light  and  he;vt  of  that  pkinet?  Estimated  strength  of  the 


2-10  ASTRONOiMY. 

it  is  computed  that  even  the  ninetieth  part  of  the  Sun's  light  exceeds  the  illuminating 
power  of  8000  full  moons,  which  would  be  abundantly  sufficient  for  all  the  purposes  of 
fife. 

498.  The  telescopic  appearance  of  Saturn  is  unparalleled.     It 
is  even  more  interesting  than  Jupiter,  with  all  his  moons  and 
belts.      That  which   eminently   distinguishes   this   planet   from 
every  other  in  the  system,  is  a  magnificent  zone  or  ring,  encir- 
cling it  with  perpetual  light. 

The  adjoining  out  is  an  excel-  TELESCOPIC  VIEW  OF  SATURN. 

lent  representation  of  Saturn 
as  seen  through  a  telescope. 
The  oblateness  of  the  planet  is 
easily  perceptible,  and  his 
shadow  can  be  seen  upon  the 
rings  back  of  the  planet.  The 
shadow  of  the  rings  may  also 
be  seen  running  across  his  disc. 
The  writer  has  often  seen  the 
opening  between  the  body  of 
the  planet  and  the  interior 
ring  as  distinctly  as  it  appears 
to  the  student  in  the  cut.  Un- 
der very  powerful  telescopes, 
these  rings  are  found  to  be 
again  subdivided  into  an  in- 
definite number  of  concentric  circles,  one  within  the  other,  though  this  is  considered 
doubtful  by  Sir  John  Herschel. 

499.  The  light  of  the  ring  is  more  brilliant  than  the  planet 
itself.     It  turns  around  its  center  of  motion  in   the  same  time 
that  Saturn   turns  on   its  axis.     When   viewed   with  a  good 
telescope,  it  is  usually  found  to  consist  of  two  concentric  rings, 
divided  by  a  dark  band. 

It  has  been  ascertained,  however,  that  these  rings  are  again  subdivided;  the  third 
division  was  distinctly  seen  by  Prof.  Encke,  on  the  25th  of  April,  1837,  and  also  by  Mr. 
Lassel,  on  the  7th  of  September,  1843,  at  his  observatory  near  Liverpool,  England.  Six 
different  rings  were  seen  at  Rome,  in  Italy,  on  the  night  of  the  29th  of  May,  1833.  And 
more  recent  observations  by  Professor  Bond,  of  Cambridge,  have  led  to  the  conclusion 
that,  in  all  probability,  these  wonderful  rings  are^«irf  /  It  is  well  known  that  under  tho 
most  powerful  instruments  they  seem  to  be  almost  indefinitely  subdivided. 

500.  As  our  view  of  the  rings  of  Saturn  is   generally  an 
oblique  one,  they  usually  appear  elliptical,  and  never  circular. 
The  ellipse  seems  to  contract  for  about  7^-  years,  till  it  almost 
entirely  disappears,  when  it  begins  to  expand  again,  and  con- 
tinues to  enlarge  for  7£  years,  when  it  reaches  its  maximum  of 
expansion,  and  again  begins  to  contract.     For  fifteen  years,  the 
part  of  the  rings  toward  us  seems  to  be  thrown  up,  while  for  tho 

solar  radiance?  498.  Telescopic  appearance  of  Saturn?  For  what  distinguished': 
499.  Comparative  light  of  his  rings?  Time  of  rotation  around  the  planet?  How  does  it 
asuu'Jy  appear?  What  further  discoveries?  500.  What  the  general  apparent  ligurt 
of  the  rings?  Why  elliptical  ?  What  periodic  variat  on  of  expansion  ?  Of  inclination  V 
When  nearly  invisible? 


THE    PRIMARY    PLANETS JUPITER    AND    SATURN.       24! 

next  fifteen  it  appears  to  drop  lelow  the  apparent  center  of  the 
planet  ;  and  while  shifting  from  one  extreme  to  the  other,  the 
rings  become  almost  invisible,  appearing  only  as  a  faint  line  of 
light  running  from  the  planet  in  opposite  directions.  The  ring? 
vary  also  in  their  inclination,  sometimes  dipping  to  the  right, 
and  at  others  to  the  left. 


TELESCOPIC  PHASES   OP  THE  RINGS  OP  SATURN. 


The  above  is  a  good  representation  of  the  various  inclin-ations  and  degrees  of  expan 
sion  of  the  rings  of  Saturn,  during  his  periodic  journey  of  80  years 


PERPENDICULAR  VIEW  OF  THE  RINGS  OF  SATURN. 


501.  The    rings   of   the 
planet  are  always  directed 
more   or    less   toward    the 
Earth,  and   sometimes   ex- 
actly toward  us  ;    so  that 
we  never  see  them  perpen- 
dicularly, but  always  either 
exactly    edgewise,     or    ob- 
liquely, as  shown  in  the  last 
figure.     Were   either   pole 
of  the  planet  exactly  toward 
us,  we  should  then  have  a 
perpendicular  view  of  the 
rings,  as  shown  in  the  ad- 
joining cut. 

502.  The  various  phases  of  Saturn's  rings  are  explained  by 
the  facts  that  his  axis  remains  parallel  to  itself  (see  following 
cut),  with  an  uniform  inclination  to  the  plane  of  his  orbit,  which 
is  very  near  the  ecliptic  ;  and  as  the  rings  revolve  over  his 
equator,  and  at  right  angles  with  his  axis,  they  also  remain 
parallel  to  themselves.     The  revolution  of  the  planet  about  the 
Earth  every  30  years,  must  therefore  bring  first  one  side  of  the 
-ings  to  view,  and  then  the  other — causing  all  the  variations  of 
expansion,  position,  and  inclination  which  the  rings  present. 


fiOl.  How  are  the  rings  situated  with  respect  to  the  Earth?  How  would  they  f.ppenr  i? 
either  pole  of  Saturn  -were  toward  us?  5o2.  How  are  the  various  phases  of  Saturn  t 
fings  accounted  for? 


242 


ASTRONOMY. 


8ATDRJJ  AT  BI-FFrrn,T  POINTS  IN  III*  ORBIT. 


Here  observe,  first,  that  the  axis  of  Saturn,  like  those  of  all  the  other  planets,  remans 
permanent,  OTJHiroUfi  with  itself;  and  as  the  rings  are  in  the  plane  of  his  equator,  and 
at  right  angles  with  his  axis,  they  also  must  remain  parallel  to  themselves,  whatever 
position  the  planet  may  occupy  in  its  orbit. 

This  being  the  case,  it  is  obvious  that  while  the  planet  is  passing  from  A  to  E,  the  Sun 
will  shine  upon  the  under  or  south,  side  of  the  rings  ;  and  while  he  passes  from  E  to  -A 
again,  upon  the  upper  or  nortli  side ;  and  as  it  requires  about  30  years  for  the  planet 
to  traverse  these  two  semicircles,  it  is  plain  that  the  alternate  day  and  night  on  the  rings 
will  be  15  years  each. 

A  and  E  are  the  equinoctial,  and  C  and  Q-  the  solstitial  points  in  the  orbit  of  Saturn. 
At  A  and  E  the  rings  arc  edgewise  toward  the  Sun,  and  also  toward  the  Earth,  provided 
Saturn  is  in  opposition  to  the  Sun.  To  an  observer  on  the  Earth,  the  rings  will  seem  to 
expand  from  A  to  C,  and  to  contract  from  C  to  E.  So,  also,  from  E  to  G,  and  from  G  to 
A.  Again  :  from  A  to  E  the  front  of  the  rings  will  appear  above  the  planet's  center,  and 
from  E  to  A  below  if.. 

The  rings  of  Saturn  were  invisible,  as  rings,  from  the  22d  of  April,  1848,  to  the  19th  of 
January,  1S49.  He  came  to  his  equinox  September  7, 1848  ;  from  which  time  to  February, 
1856,  his  rings  continued  to  expand.  ¥rom  that  time  to  June,  18(53,  they  contracted, 
until  he  reached  his  other  equinox  at  E.  and  the  rinjrs  became  invisible.  From  Juno 
18GS,  to  September,  1870,  they  will  again  expand ;  and  from  September,  1870,  to  March, 
1877,  they  will  contract,  when  he  will  be  at  the  equinox  passed  September  7, 1848,  or 
29 14  years  before. 

The  writer  has  often  seen  the  rings  of  Saturn  in  different  stages  of  expansion,  and  con- 
traction, and  once  when  they  were  almost  directly  edgewise  toward  the  Earth.  At  that 
tune  (January,  1849),  they  appeared  as  a  bright  line  of  light,  as  represented  at  A  and 
E,  in  the  tirst  cut  on  the  preceding  page. 

503.  The  dimensions  of  the  rings  of  Saturn  may  be  stated  in 
round  numbers  as  follows  : 

Miles. 

Distance  from  the  body  of  the  planet  to  the  first 

ring 19,000 

Width  of  interior  ring 17,000 

Space  between  the  interior  and  exterior  rings    .     .  2,000 

Width  of  exterior  ring 10,500 

Thickness  of  the  rings 100 


b08.  State  the  distances  and  dimensions  of  his  rings,  beginning  at  the  body  of  the  plnnrt, 
K*  '.Kissing  outward?     What  additional  statistics  from  licrschcl? 


THE    PRIMAK1'    PLAJNETS JUP1TEB.    AND    SATURN.       243 

In  c  recent  work,  entitled  "  The  New  Theory  of  Creation  and  Deluge,"  it  is  predictor. 
I*. at,  at  some  future  time,  the  fluid  rings  of  Saturn  may  descend  and  deluge  the  pla.net, 
>-.-  ou  s  was  deluged  in  the  days  of  Noah.  Sir  David  Brewster  says  : — "  Mr.  Otto  Strure 
r,  (i  Mr.  Bond  have  lately  studied  with  the  great  Munich  telescope  at  the  Observatory 
of  1'ulk.oway,  the  third  ring  of  Saturn,  which  Mr.  Dassels  and  Mr.  Bond  discovered  to 
be  fl  Jd.  These  astronomers  are  of  opinion  that  this  fluid  ring  is  not  of  very  recent 
formation,  and  that  it  is  not  subject  to  rapid  change ,  and  they  have  come  to  the  extra- 
ord  .jury  conclusion  that  the  inner  border  of  the  ring  has,  since  the  time  of  Huyprens, 
bee  i  gradually  approaching  the  body  of  Saturn,  and  that  we  may  expect,  sooner  or 
<f»t(  r,  perhaps  in  some  dozen  of  years,  to  see  the  rings  united  with  the  body  of  the  planet." 

M4.  The  rings  of  Saturn  serve  as  reflectors  to  reflect  the 
HjrM  of  the  Sun  upon  his  disc,  as  our  Moon  reflects  the  light  to 
the  Earth.  In  his  nocturnal  sky,  they  must  appear  like  two 
ffo^ereous  arches  of  light,  bright  as 

NIGHT  SCHSB   UPON   SATORN. 

rhc  full  moon,  and  spanning  the 
•vhole  heavens  like  a  stupendous 
rainbow. 

In  the  annexed  cut,  the  beholder  is  supposed 
ro  be  situated  some  30°  north  of  the  equator  of 
Saturn,  and  looking  directly  south.  The  skadow 
of  the  planet  is  seen  travelling  up  the  arch  as 
the  night  advances,  while  a  New  Moon  is  shown 
'n  .the  west,  and  a  FiM  Moon  in  the  east  at  tho 
same  time. 

505.  The  two  rings  united  are  nearly  13  times  as  wide  as  the 
diameter  of  the  Moon  ;  and  the  nearest  is  only  y^th  as  far  from 
the  planet  as  the  Moon  is  from  us. 

The  two  rings  united  are  27,500  miles  wide  ;  which-i-2160  the  moon's  diameter=12_7_ 
3o  240,000  miles,  the  Moon's  .distance  •+•  19,000  the  distance  of  Saturn's  interior 
ring=12ff. 

At  the  distance  of  only  19,000  miles,  our  Moon  would  appear  some  forty  times  as  large 
as  she  does  at  her  present  distance.  How  magnificent  and  inconceivably  grand,  then, 
must  these  vast  rings  appear,  with  a  thousand  tiuies  the  Moon's  magnitude,  and  only 
one-twelfth  part  of  her  distance ! 

506.  The  periodic  time  of  Saturn  being  nearly  thirty  years, 
his  motion  eastward  among  the  stars  must  be  very  slow,  amount- 
ing to  only  12°  a  year,  or  one  sign  in  2£  years.     It  will  be  easy, 
therefore,  having  once  ascertained  his  position,  to  watch  his  slow 
progress  eastward  year  after  year,  as  he  performs  his  vast  circuit 
around  the  heavens. 

MOONS  OF  SATURN. 

507.  Besides   the   magnificent   rings   already  described,    th 
telescope  re  veals  eight  satellites  QI  moons,  revolving  around  Saturn. 
But  these  are  seen  only  with  good  instruments,  and  under  favor- 
able circumstances. 

604.  What  purpose  do  the  ring3  of  Saturn  serve?  How  appear  in  his  evening  sky? 
605.  Width  of  two  rings, as  compared  with  Moon  ?  Distance?  Demonstrate  both.  How 
would  our  Moon  appear  at  the  distance  of  Saturn's  rings?  50(5.  Eastward  motion  of 
Saturn?  Uow  traced?  507.  Muous  of  Saturn  ?  How  seen?  Best  time  for  observing? 

B.G.  11 


214  ASTRONOMY. 

SATELLITES  OF  SATURH. 

The  best  time  for  observ- 
ing them  is  when  the  planet 
is  at  his  equinoxes,  and  his 
rings  are  nearly  invisible. 

In  January,  1849,  the  author  saw  five 

of  these  satellites,  as  represented  in  the  adjoining  cut.  The  rings  appeared  only  as  a  line 
->f  light  extending  each  way  from  the  planet,  and  the  satellites  were  in  the  direction  of 
the  line,  at  different  distances,  as  here  represented 

508.  These  satellites  all  revolve  eastward  with  the  rings  of 
the  planet,  in  orbits  nearly  circular,  and,  with  the  exception  of 
the  eighth,  in  the  plane  of  the  rings.  Their  mean  distances, 
respectively,  ii*om  the  planet's  center  are  from  123,000  to 
2,366,000  miles  ;  and  their  periods  from  22  hours  to  79  days, 
according  to  their  distances. 

The  distances  and  periods  of  the  satellites  of  Saturn  are  as  follows  : 

Distance  in  mile*.  Periodic  time*.  Distance  in  miles.        Periodic  times. 


1st 118,000 0  day  22*  hours 

2d  152,000 1    "     9 

8d   188,000 1    "    21        " 

4th 240,000 2    "17        " 


6th 886,000 4  days  12  hours 

6th 778,000 15    "     22      " 

7th 940,000 22    "      ..       "* 

8th 2,263,000 79    "       7      " 


COMPARATIVE  DISTANCES  OF  THE  MOONS  OF  SATURN. 


509.  The  most  distant  of  these  satellites  is  the  largest,  sup 
posed  to  be  about  the  size  of  Mars  ;  and  the  remainder  grow 
smaller  as  they  are  nearer  the  primary.  They  are  seldom  eclipsed, 
on  account  of  the  great  inclination  of  their  orbits  to  the  ecliptic, 
except  twice  in  thirty  years,  when  the  rings  are  edgewise  toward 
the  Sun,  The  eighth  satellite,  which  has  been  studied  more  than 
all  the  rest,  is  known  to  revolve  once  upon  its  axis  during  every 
periodic  revolution  ;  from  which  it  is  inferred  that  they  all 
revolve  on  their  respective  axis  in  the  same  manner. 

SYSTEM  OF  SATURN — NO  ECLIPSES. 

Let  the  line  A  B  represent  the  plane 

of  the  planet's  orbit,  C  D  his  axis,  and  °" 

E  F  the  plane  of  his  rings.  The  satellites 
being  in  the  plane  of  the  rings  will 
revolve  around  the  shadow  of  the  pri- 
mary, instead  of  passing  through  it,  and 
being  eclipsed. 

At  the  time  of  his  equinoxes,  however, 
when  the  rings  are  turned  toward  the 
i<un  (see  A  and  E,  cut,  page  242)  they 
must  be  in  the  center  of  the  shadow  on 

508.  The  revolutions?  Shape  and  position  of  their  orbits  ?  Distances  from  their  prl 
ttiary?  509.  Comparative  size? 


THE    PRIMARY    PLANETS JUPITER    AND    SATURN.        245 

tiic  opposite  side  ;  and  the  moons,  revolving  in  the  plane  of  the  rings,  must  pass  through 
the  shadow  at  every  revolution.  The  eighth,  however,  may  sometimes  escape,  on  account 
of  his  departure  from  the  plane  of  the  rings,  as  shown  in  the  cut. 

510.  The  theory  of  the  satellites  of  Saturn  is  less  perfect  than 
than  that  of  the  satellites  of  Jupiter.  The  difficulty  of  observ- 
ing their  eclipses,  and  of  measuring  their  elongations  from  their 
primary,  have  prevented  astronomers  from  determining,  with 
their  usual  precision,  their  mean  distances  and  revolutions.  But 
of  this  we  are  certain  :  there  is  no  planet  in  the  solar  system, 
whose  firmament  presents  such  a  variety  of  splendid  and  mag- 
nificent objects  as  that  of  Saturn. 

The  various  aspects  of  the  seren  moons,  one  rising  above  the  horizon,  while  another  is 
setting,  and  a  third  approaching  to  the  meridian ;  one  entering  into  an  eclipse,  and 
another  emerging  from  one  ;  one  appearing  as  a  crescent,  and  another  with  a  gibbous 
phase ;  and  sometimes  the  whole  of  them  shining  in  the  same  hemisphere,  in  one  bright 
assemblage  !  The  majestic  motion  of  the  rings — at  one  time  illuminating  the  sky  with 
their  splendor,  and  eclipsing  the  stars ;  at  another,  casting  a  deep  shade  over  certain 
regions  of  the  planet,  and  unveiling  to  view  the  wonders  of  the  starry  firmament,  arc 
scenes  worthy  of  the  majesty  of  the  Divine  Being  to  unfold,  and  of  rational  creatures  to 
contemplate. 

•  Such  displays  of  Wisdom  and  Omnipotence,  lead  us  to  conclude  that  the  numerous 
splendid  objects  connected  with  this  planet,  were  not  created  merely  to  shed  their  luster 
on  naked  rocks  and  barren  sands;  but  that  an  immense  population  of  intelligent  being? 
is  placed  in  those  regions,  to  enjoy  the  bounty,  and  adore  the  goodness,  of  their  great 
Creator. 


CHAPTER  VIII. 
PRIMARY  PLANETS.— URANUS  AND  NEPTUNE. 

511 .  URANUS  is  the  next  planet  in  order  from  the  Sun,  beyond 
or  above  Saturn.  To  the  naked  eye,  it  appears  like  a  star  of 
only  the  6th  or  7th  magnitude,  and  of  a  pale,  bluish  white  ;  but 
it  can  seldom  be  seen,  except  in  a  very  fine,  clear  night,  and  in 
the  absence  of  the  Moon.  Through  a  telescope,  he  exhibits  a 
small,  round,  uniformly  illuminated  disc,  without  rings,  belts,  01 
discernible  spots.  His  apparent  diameter  is  about  4",  from 
which  he  never  varies  much,  owing  to  the  smallness  of  our  orbH 
in  comparison  with  his  own. 

510.  Is  the  system  of  Saturn  well  understood?  Why  not?  Of  what  are  we  sure? 
What  scenes  must  it  present?  To  what  conclusion  must  these  phenomena  had  ua» 
511.  Portion  and  appearance  rf  Uranus?  Through  a,  telescooe  ? 


246  ASTRONOMY. 

-Sir  John  Herschel  says  he  is  without  discernible  spots,  and  yet  in  his  :ablps  h*  lays 
down  the  time  of  the  planet's  rotation  (which  could  only  be  ascertained  by  the  rotation 
of  spots  upon  the  planet's  disc;,  at  v%  hours.  This  time  is  probably  given  on  the 
minority  of  Schroeter,  and  is  marked  as  doubtful  by  Dr.  Herschel. 

512.  The  motion  of  Uranus  in  longitude  is  still  slower  than 
that  of  Saturn.     It  moves  over  but  one  degree  of  its  orbit  in 
85  days  ;  hence  he  will  be  seven  years  in  passing  over  one  sign 
or  constellation.     His  periodic  time  being  84  years  27  days,  his 
eastward  motion  can  amount  to  only  about  4°  17'  in  a  whole 
year.     To  detect  this  motion   requires  instruments  and   close 
observations.     At  this  date  (1866),  Uranus  has  made  the  entire 
circuit   of  the   heavens   since   his  discovery  in  1781;    having 
passed,  in   1865,  the  point  where  he  was  first  seen,  and  being 
now  upon  his  second  known  journey  around  the  heavens. 

It  is  remarkable  that  this  body  was  observed  as  far  back  as  1690.  It  was  seen  three 
times  by  Flamstead,  once  by  Bradley,  once  by  Mayer,  and  eleven  times  by  Lemonnier, 
who  registered  it  among  the  stars ;  but  not  one  of  them  suspected  it  to  be  a  planet. 

513.  The  inequalities  in  the  motions  of  Jupiter  and  Saturn, 
which  could  not  be  accounted  for  from  the  mutual  attractions 
of  these  planets,  led  astronomers  to  suppose  that  there  existed 
another  planet  beyond  the  orbit  of  Saturn,  by  whose  action 
these  irregularities  were  produced.     This  conjecture  was  con- 
firmed March  13th,  1781,  when  Dr.  Herschel  discovered  the 
motions  of  this  body,  and  thus  proved  it  to  be  a  planet. 

514.  The    mean    distance    of    Uranus    from    the    Sun    is 
1,828,000,000  of  miles  ;  more  than  twice  the  mean  distance  of 
Saturn.     His  sidereal  revolution  is  performed  in  84  years  and 
1  month,  and  his  motion  in  his  orbit  is  15,600  miles  an  hour. 
He  is  supposed  to  have  a  rotation  on  his  axis,  in  common  with 
the  other  planets  ;  but  astronomers  have  not  yet  been  able  to 
obtain  any  ocular  proof  of  such  a  motion 

515.  His  diameter  is  estimated  at  36,000  miles  ;  which  would 
make  his  volume  more  than  80  times  larger  than  the  Earth's. 
To  his  inhabitants,  the  Sun  appears  only  the  ^j  part  as  large 
as  he  does  to  us  ;  and  of  course  they  receive  from  him  only  that 
small  proportion  of  light  and  heat.     It  may  be  shewn,  however, 
that  the  ^-g   part  of  the  Sun's  light  exceeds  the  illuminating 
power  of  800  full  moons.     This,  added  to  the  light  they  must 
receive  from   their   six  satellites,  will  render  their  days  and 
nights  far  from  cheerless. 

512.  His  motion  in  longitude  ?  Periodic  time  ?  Angular  motion  per  year  ?  How  far 
h.is  he  been  traced  since  his  discovery?  When  complete  his  revolution?  Was  he  ever 
ceen  previous  to  !<;>..?  By  whom?  Why  are  they  not  the  discoverers,  then  ?  513.  Was 
his  existence  suspected  previous  to  1781  ?  What  ground  for  the  suspicion?  How  prove J 
to  be  a  pifinet ?  514.  Mean  distance?  Sid ereal  revolution?  Hourly  motion  in  orbit  t 
Eolation  on  axis  ?  515.  Diameter  ?  V<riur-»  Light  aod  heat?  ILie 


THE    PRIMARY    PLANETS URANUS    AND    NEPTUNE.     247 

516.  Uranus  is  attended  by  six  moons  or  satellites,  which 
revolve  about  him  in  different  periods,  and  at  various  distances. 
Four  of  them  were  discovered  by  Sir  William  Herschel,  and  two 
by  his  sister,  Miss  Caroline  Herschel.  It  is  possible  that  others 
remain  yet  to  be  discovered. 

Most  of  the  satellites  revolve  from  east  to  west  around  their 
primaries;  but  the  satellites  of  Uranus  are  an  exception  to  this 
rule.  Their  orbits  are  inclined  to  the  plane  of  the  ecliptic  79°, 
being  little  less  than  a  right  angle;  and  their  motion  in  their 
orbits  is  retrograde,  that  is,  from  east  to  west. 

The  distance  from  the  planet,  and  the  periodic  times  of  the  satellites  of  Uranus* 
respectively,  are  as  follows:— 

Dlst  in  mile*.  Periodic  tinier  Dist  in  milot.  Periodic  times. 

•     D.      H.  Tt.       H. 

1 120,000 2    1214... 380,000 18    11 

2 171,000 4      85 777,000 38      2 

8 288,000 8    1716 1,556,000 107    16 


NEPTUNE. 

517  This  is  the  most  distant  of  the  primary  planets,  and  in 
some  respects  one  of  the  most  interesting.  It  is  about  35,000  miles 
in  diameter,  is  situated  at  the  mean  distance  of  2,862,000,000 
miles  from  the  Sun,  and  revolves  around  him  in  164  years.  So 
remote  is  this  newly-discovered  member  of  the  solar  system,  that 
for  a  body  to  reach  it,  moving  at  railroad  speed,  or  30  miles  an 
hour,  would  require  more  than  twenty  thousand  years  ! 

518.  The  circumstances  of  the  discovery  of  this  planet  are  at 
once  interesting  and  remarkable.  Such  is  the  regularity  of  the 
planetary  motions,  that  astronomers  are  enabled  to  predict,  with 
great  accuracy,  their  future  places  in  the  heavens,  and  to  con- 
struct tables,  exhibiting  their  positions  for  ages  to  come.  Soon 
after  the  discovery,  of  Uranus,  in  1781,  his  orbit  was  computed, 
and  a  table  constructed  for  determining  his  future  positions  in 
the  heavens,  but  instead  of  following  the  prescribed  path,  or 
occupying  his  estimated  positions,  he  was  found  to  be  yielding  to 
some  mysterious  and  unaccountable  influence,  under  which  he 
was  gradually  leaving  his  computed  orbit,  and  failing  to  meet 
conditions  of  the  tables. 


510.  Number  of  Moons?  By  whom  discovered?  Is  it  certain  that  Uranus  hus  six 
satellites?  Why  doubtful?  517.  Distance  and  diameter  of  Neptune?  Period?  How 
long  to  pass  from  the  Sun  to  it  at  railroad  speed  ?  518.  What  remarkable  «ircm» 
Stances  respecting  its  discovery  ?  Perturbation  ? 


248  ASTRONOMY. 

519.  At  first  this  discrepancy  between  the  observed  and  the 
estimated  places  of  Uranus,  was  charged  upon  the  tables,  and  a 
new  orbit  and  new  tables  were  computed,  which  it  was  thought 
could  not  fail  to  represent  the  future  places  of  the  planet.     But 
these  also  seemed  to  be  erroneous,  as  it  was  soon  discovered  tha  t 
the  computed  and  observed  places  did  not  agree,  and  the  differ- 
ence was  becoming  greater  and  greater  every  year.     This  was 
an  anomaly  in  the  movements  of  a  planetary  body.     It  was  not 
strange  that  it  should  be  subject  to  perturbations,  from  the  attrac- 
tive influence  of  the  large  planets  Jupiter  arid  Saturn,  as  these 
were  known  to  act  upon  him,  as  well  as  upon  each  other,  and 
the  smaller  planets,  producing  perturbations  in  their  orbits,  but 
all  this  had  been  taken  into  the  account  in  constructing  the 
tables,  and  still  the  planet  deviated  fi*>m  its  prescribed  path. 

520.  To  charge  the  discrepancy  to  the  tables,  was  no  longer 
reasonable,  though  it  was  thought  perhaps  sufficient  allowance 
had  not  been  made,  in  their  computation,  for  the  disturbing  influ- 
ence of  Jupiter  and  Saturn.     To  determine  this  question,  M.  Le- 
verrier,  of  Paris,  undertook  a  thorough  discussion  of  the  sub- 
ject, and  soon  ascertained  that  the  disturbing  influence  upon 
Uranus  of  all  the  known  planets,  was  not  sufficient  to  account 
for  the  anomalous  perturbations  already  described,  and  that  they 
were  probably  caused  by  some  unknown  planet,  revolving  beyond 
the  orbit  of  Uranus.     From  the  amount  and  effect  of  this  dis- 
turbing influence  from  an  unknown  source,  the  distance,  magni- 
tude? and  position  of  the  imaginary  planet  were  computed. 

521.  At  this  stage  of  the  investigation,  Leverrier  wrote  to 
his  friend,  Dr.  Galle,   of  Berlin,   requesting  him   to  direct  his 
telescope  to  that  part  of  the  heavens  in  which  his  calculations 
had  located  the  new  planet,  when  lo  1  there  he  lay,  a  thousand 
millions  of  miles  beyond  the  orbit  of  Uranus,  and  yet  within  less 
than  one  degree  of  the  place  pointed  out  by  Leverrier  !     This 
was  on  the  1st  of  September,  1846. 

522.  While  M.  Leverrier  was  engaged  in  his  calculations  at 
Paris,  Mr.  Adams,  a  young  mathematician  of  Cambridge,  Eng- 
land, was  discussing  the  same  great  problem,  and  had  arrived  at 
similar  results  even  before  M.  Leverrier,  though  entirely  igno- 
rant of  each  other's  labors  or  conclusions.     This  seems  to  estab- 


519.  To  what  attributed  at  first?  What  done  to  correct?  What  then?  520.  What 
next  undertaken,  and  by  whom  ?  What  result  and  conclusion  ?  521.  What  remarkable 
computation  and  letter?  Result  of  Dr.  Galle's  search?  522.  Who  else  investigating 
the  subject  at  the  same  time?  His  conclusions ?  What  fact  does  this  establish?  Why 
not  Adorns  the  discoverer? 


THE  PRIMARY  STARS SATURN  AND  NEPTU^ii.    249 

Hsh  the  fact,  that  the  new  planet  was  discovered  by  calculation, 
though'  the  failure  of  Mr.  Adams  to  publish  his  conclusions,  cut 
off  his  right  to  the  honor  of  the  discovery. 

523.  Since  the  discovery  of  this  planet,  it  has  been  ascertained 
that  it  was  seen  as  far  back  as  1795,  though  supposed  to  be  a 
fixed  star,  and  catalogued  as  such  ;  and  that  all  the  irregulari- 
ties of  Uranus,  with  which  astronomers  were  so  much  perplexed, 
are  perfectly  accounted  for  by  the  influence  of  the  new  planet. 

524.  Neptune  is  attended  by  but  one  satellite,  so  far  as   is 
known.     It  was  discovered  by  Mr.   Lassell,   of  Star-field,  near 
Liverpool,  October  12,  1846.     It  revolves  around  its  primary 
in  5  days  and  21  hours,  at  a  distance  of  236,000  miles  from  the 
planet's  centre.     Its  orbit  is  inclined  to  the  plane  of  the  ecliptic 
29°,  and  its  motion  in  its  orbit  is  retrograde,  like  the  direction 
of  the  satellites  of  Uranus. 


CHAPTER  IX. 

OOMET^-THEIR  NATURE,  MOTIONS,  ORBITS,  &o. 

525.  COMETS,  whether  viewed  as  ephemeral  meteors,  or  as 
substantial  bodies,  forming  a  part  of  the  solar  system,  are  objects 
of  no  ordinary  interest.     When,  with  uninstructed  gaze,  we  look 
upwards,  to  the  clear  sky  of  evening,  and  behold,  among  the 
multitudes  of  heavenly  bodies,  one,  blazing  with  its  long  train 
of  light,  and  rushing  onward  towards  the  center  of  our  system, 
we  insensibly  shrink  back  as  if  in  the  presence  of  a  supernatural 
being.     But  when,   with  the  eye  of  astronomy,   we  follow  it 
through  its  perihelion,  and  trace  it  far  off,  beyond  the  utmost 
verge  of  the  solar  system,  till  it  is  lost  in  the  infinity  of  space, 
not  to  return  for  centuries,  we  are  deeply  impressed  with  a  sense 
of  that  power   which   could   create  and  set  in  motion   such 
bodies. 

526.  Comets  are  distinguished  from  the  other  heavenly  bodies, 
by  their  appearance  and  motion.     The  appearance  of  the  planets 

528.  Has  Neptune  ever  been  seen  prior  to  1846?  What  supposed  to  be?  Does  it 
account  for  the  perturbation  of  Uranus?  524.  lias  Neptune  a  satellite?  When,  and 
by  whom  discovered?  What  said  of  rings?  525.  Subject  of  this  chapter?  How 
•jotneto  regar led  by  the  uninstructed?  By  the  astronomer?  526.  How  distinguishe-J 


250  ASTRONOMY. 

is  globular,  and  their  motion  around  the  Sun  is  nearly  in  the 
same  plane,  and  from  west  to  east  ;    but  the  comets  have 
variety  of  forms,  and  their  orbits  are  not  confined  to  any  par- 
ticular part  of  the  heavens  ;  nor  do  they  observe  any  one  general 
direction. 

The  orbits  of  the  planets  approach  nearly  to  circles,  while 
those  of  the  comets  are  very  elongated  ellipses.  A  wire  hoop, 
for  example,  will  represent  the  orbit  of  a  planet.  If  two  oppo- 
site sides  of  the  same  hoop  be  extended,  so  that  it  shall  be  long 
and  narrow  it  will  then  represent  the  orbit  of  a  comet.  Tho 
Sun  is  always  in  one  of  the  foci  of  the  comet's  orbit. 


ORBIT  0V  A  OOMKT. 


Here  it  will  be  seen  that  the  orbit  is  very  eccentric,  that  the  perihelion  point  is  very 
near  the  Sun,  and  the  aphelion  point  very  remote. 

There  is,  however,  a  practical  difficulty  of  a  peculiar  nature  which  embarrasses  the 
solution  of  the  question  as  to  the  form  of  the  cometary  orbits.  It  so  happens  that  the 
only  part  of  the  course  of  a  comet  which  can  ever  be  visible,  is  a  portion  throughout 
which  the  ellipse,  the  parabola,  and  hyperbola,  so  closely  resemble  each  other,  that  no 
observations  can  be  obtained  with  sufficient  accuracy  to  enable  us  to  distinguish  them. 
In  fact,  the  observed  path  of  any  comet,  while  visible,  may  belong  either  to  an  ellipse, 
parabola,  or  hyperbola. 

527.  That  part  which  is  usually  brighter,  or  more  opaque,  than 
the  other  portions  of  the  comet,  is  called  the  nucleus.  This  is 
surrounded  by  an  envelope,  which  has  a  cloudy,  or  hairy  appear- 
ance. These  two  parts  constitute  the  body,  and,  in  many 
instances,  the  whole  of  the  comet.  Most  of  them,  however,  are 
attended  by  a  long  train,  called  the  tail ;  though  some  are  with- 
out this  appendage,  and  as  seen  by  the  naked  eye,  are  not  easily 
distinguished  from  the  planets.  Others  again,  have  no  apparent 
nucleus,  and  seem  to  be  only  globular  masses  of  vapor. 

Nothing  is  known  with  certninty  of  the  composition  of  these  bodies.  The  envelope 
appears  to  be  nothing  more  than  vapor,  becoming  more  luminous  and  transparent  when 

trom  other  bodies?  Form?  Orbits?  What  practical  difficulty  mentioned?  527. 
What  is  the  nucleus  of  a  comet?  The  envelope  ?  The  tail?  Have  all  cornets  thes* 
three  parts?  Do  we  understand  of  what  they  are  composed?  What  evidence  of  then 
<vxtreme  tenuity? 


COMETS THEIR    NATURE,    MOTIONS,    ORBITS,  ETC.      251 

approaching  the  Sun.  As  the  comets  pass  between  us  and  the  fixed  stars,  their  envelope  j 
and  tails  are  so  thin,  that  stars  of  very  small  magnitude  may  be  seen  through  them. 
Some  comets,  hiving  no  nucleus,  are  transparent  throughout  their  whole  extent. 

528.  The  nucleus  of  a  comet  sometimes  appears  opaque,  and 
it  then   resembles   a  planet.     Astronomers,   however,   are  not 
agreed  upon  this  point.     Some  affirm  that  the  nucleus  is  always 
transparent,  and  that  comets  are  in  fact  nothing  but  a  mass  of 
vapor,  more  or  less  condensed  at  the  center.    By  others  it  is  main- 
tained  that   the   nucleus   is  sometimes  solid  and  opaque.     It 
seems  probable,  however,  that  there  are  three  classes  of  comets, 
viz.  ;    1st.  Those  which   have   no   nucleus,    being   transparent 
throughout  their  whole  extent  ;  2d.  Those  which  have  a  trans- 
parent nucleus  ;  and,  3d.  Those  having  a  nucleus  which  is  solid 
and  opaque. 

529.  A  comet,  when  at  a  distance  from   the  Sun,  viewed 
through  a  good  telescope,  has  the  appearance  of  a  dense  vapor 
surrounding  the  nucleus,  and  sometimes  flowing  far  into  the 
regions  of  space.     As  it  approaches  the  Sun,  its  light  becomes 
more  brilliant,  till  it  reaches  its  perihelion,  when  its  light  is  more 
dazzling  than  that  of  any  other  celestial  body,  the  Sun  excepted. 
In  this  part  of  its  orbit  are  seen  to  the  best  advantage  the  phe- 
nomena of  this  wonderful  body,  which  has,  from  remote  antiquity, 
been  the  specter  of  alarm  and  terror. 

530.  The  luminous  train  of  a  comet  usually  follows  it,  as  it 
approaches  the  Sun,  and  goes  before  it,  when  the  comet  recedes 
from  the  Sun  ;  sometimes  the  tail  is  considerably  curved  towards 
the  region  to  which  the  comet  is  tending,  and  in  some  instances, 
it  has  been  observed  to  form  a  right  angle  with  a  line  drawn 
from  the  Sun  through  the  center  of  the  comet.     The  tail  of  the 
comet  of  1744,  formed  nearly  a  quarter  of  a  circle  ;  that  of 
1689  was  curved  like  a  Turkish  sabre.     (Map  IX.,  Fig.  73.) 
Sometimes  the  same  comet  has  several  tails.     That  of  1744  had, 
at  one  time,  no  less  than  six,  which  appeared  and  disappeared  in 
a  few  days.     (See  Map  IX.,  Fig.  74.)     The  comet  of  1823 
had,  for  several  days,  two  tails  ;  one  extending  towards  the  Sun, 
and  the  other  in  the  opposite  direction. 

531.  Comets,  in  passing  among  and  near  the  planets,  are  ma- 
terially drawn  aside  from  their  courses,  and  in  some  cases  have 
their  orbits  entirely  changed.     This  is  remarkably  true  in  regard 

528.  What  difference  of  opinion  respecting  t'e  nucleus  of  comets?    What  probable 

solution  ?        529.  How  do  they  appear  when  viewed  through  a  telescope  at  a  distance 

from  the  Sun?     As  it  approaches  him?     Where  seen  to  best  advantage?        530.  UsufiJ 

lirection   of  the  trains   of  comets?     Other  positions?     Comet  of  1744?     Of  Ib89?     O/ 

S23?        531.  Influence  of  attraction  upon  comets?     Illustrations?     Comet  of  1770  ? 


252  ASTRONOMY. 

to  Jupiter,  which  seems  by  some  strange  fatality  to  be  constantly 
in  their  way,  and  to  serve  as  a  perpetual  stumbling-block  to 
them. 

"  The  remarkable  comet  of  1770,  which  was  found  by  Lexell  to  revolve  in  a  moderate 
ellipse,  in  a  period  of  about  five  years,  actually  got  entangled  among  the  satellites  of 
Jupiter,  and  thrown  out  of  its  orbit  by  the  attractions  of  that  planet,"  and  has  not  been 
heard  of  since.— fferschel,  p.  310.  By  this  extraordinary  rencontre,  the  motions  of 
Jupiter's  satellites  suffered  not  the  least  perceptible  derangement ;  a  sufficient  proof  of 
the  aeriform  nature  of  the  comet's  mass. 

532.  It  is  clear  from  observation,  that  comets  contain  very 
little  matter.  For  they  produce  little  or  no  effect  on  the  motion 
of  the  planets  when  passing  near  those  bodies  ;  it  is  said  that  a 
comet,  in  1454,  eclipsed  the  Moon  ;  so  that  it  must  have  been 
very  near  the  Earth  ;  yet  no  sensible  effect  was  observed  to  be 
produced  by  this  cause,  upon  the  motion  of  the  Earth  or  the 
Moon. 

The  observations  of  philosophers  upon  comets,  have  as  yet  detected  nothing  of  their 
nature.  Tycho  Brahe  and  Appiar.  supposed  their  tails  to  be  produced  by  the  rays  of  the 
Sun  transmitted  through  the  nucleus,  which  they  supposed  to  be  transparent,  and  to  ope- 
rate as  a  lens.  Kepler  thought  they  were  occasioned  by  the  atmosphere  of  the  comet, 
driven  off  by  the  impulse  of  the  Sun's  rays.  This  opinion,  with  some  modification,  was 
also  maintained  by  Euler.  Sir  Isaac  Newton  conjectured  that  they  were  a  thin  vapor, 
rising  from  the  heated  nucleus,  as  smoke  ascends  from  the  Earth ;  while  Dr.  Hamilton 


supposed  them  to  oe  streams  of  electricity. 
"That  the  luminous  part  of  a  comet,"  s 


says  Sir  John  Herschel,  "  is  something  in  the 
nature  of  a  smoke,  fog,  or  cloud,  suspended  in  a  transparent  atmosphere,  is  evident  from 
a  fact  which  has  been  often  noticed — viz.,  that  the  portion  of  the  tail  where  it  comes  up 
to,  and  surrounds  the  head,  is  yet  separated  from  it  by  an  interval  less  luminous  ;  as  we 
often  see  one  layer  of  clouds  laid  over  another  with  a  considerable  clear  space  between 
them."  And  again  :  "  It  follows  that  these  can  only  be  regarded  as  great  masses  of  thin 
vapor,  susceptible  of  being  penetrated  through  their  whole  substance  by  the  sunbeams." 

533.  Comets  have  always  been  considered  by  the  ignorant  and 
superstitious,  as  the  harbingers  of  war,  pestilence,  and  famine. 
Nor  has  this  opinion  been,  even  to  this  day,  confined  to  the 
unlearned.     It  was  once  universal.     And  when  we  examine  the 
dimensions  and  appearances  of  some  of  these  bodies,  we  cease 
to  wonder  that  they  produced  universal  alarm. 

According  to  the  testimony  of  the  early  writers,  a  comet  which  could  be  seen  in  day- 
light with  the  naked  eye,  made  its  appearance  43  years  before  the  birth  of  our  Saviour. 
This  date  was  just  after  the  death  of  Caesar,  and  by  the  Romans,  the  comet  was  believed 
to  be  his  metamorphosed  soul,  armed  with  fire  and  vengeance.  This  comet  is  again  men- 
tioned as  appearing  in  1106,  and  then  resembling  the  Sun  in  brightness,  being  of  a  great 
eize,  and  having  an  immense  tail.  In  the  year  1402,  a  comet  was  seen,  so  brilliant  as  to 
be  discerned  at  noon-day. 

534.  In  1456,  a  large  comet  mads  its  appearance.     It  spread 
a  wider  terror  than  was  ever  known  before.     The  belief  was  very 
general,   among  all   classes,  that  the  comet  would  destroy  the 
Earth,  and  that  the  Day  of  Judgment  was  at  hand  I 

632.  What  said  of  their  ]  hysical  natures  ?  Opinion  of  Tycho  Brahe  ?  Of  Kepler  and 
Euler?  Of  Newton  and  Dr.  Hamilton]  Of  Sir  John  Herschel?  633.  How  have  corneta 
Usually  been  regarded  by  :he  ignorant?  What  remarkable  comet  mentioned?  53-t. 
What  comet  in  145G  ?  EFact  of  its  appearance  ?  Has  it  appeared  since  ?  Its  period  ? 


COMETS THEIR    NATURE,    MOTIONS,    ORBITS,    ETC.      253 

The  same  comet  appeared  again  in  the  years  1531,  1607, 1682, 
1758  and  1835.  It  passed  its  perihelion  in  November,  1835, 
and  will  re-appear  every  75^  years  thereafter. 

At  the  time  of  the  appearance  of  this  comet,  the  Turks  extended  their  victorious  arms 
r,cror:3  the  Hellespont,  and  seemed  destined  to  overrun  all  Europe.  This  added  not  a 
.ittle  to  the  general  gloom.  Under  all  these  impressions,  the  people  seemed  totally  regard- 
less of  the  present,  and  anxious  only  for  the  future.  The  Romish  Church  held  at  this 
time  unbounded  sway  over  the  lives,  and  fortunes,  and  consciences  of  men.  To  prepare 
the  world  for  its  expected  doom,  Pope  Calixtus  III.  ordered  the  Ave  Maria  to  be  repeated 
three  times  a  day,  instead  of  two.  He  ordered  the  church  bells  to  be  rung  at  noon, 
which  was  the  origin  of  that  practice,  so  universal  in  Christian  churches.  To  the  Avc 
Maria,  the  prayer  was  added — "  Lord  !  save  us  from  the  Devil,  the  Turk  and  the  Comet ;" 
and  once,  each  day,  these  three  obnoxious  personages  suffered  a  regular  excommuni- 
lation.  , 

The  Pope  and  clergy  exhibiting  such  fear,  it  is  not  a  matter  of  wonder  that  it  became 
the  ruling  passion  of  the  multitude.  The  churches  and  convents  were  crow  'ed  for  con- 
fession of  sins ;  and  treasures  uncounted  were  poured  into  the  Apostolic  chau  ber. 

The  comet,  after  suffering  some  months  of  daily  cursing  and  excommunicati  >n,  began 
to  show  signs  of  retreat,  and  soon  disappeared  from  those  eyes  in  which  it  i  >und  nc 
favor.  Joy  and  tranquillity  soon  returned  to  the  faithful  subjects  of  the  Pope,  bu  not  sc 
their  money  and  lands.  The  people,  however,  became  satisfied  that  their  lives,  and  the 
safety  of  the  world,  had  been  cheaply  purchased.  The  Pope,  who  had  achieved  so  signal 
a  victory  over  the  monster  of  the  sky,  had  checked  the  progress  of  the  Turk,  and  kept, 
for  the  present,  his  Satanic  majesty  at  a  safe  distance ;  while  the  Church  of  Rome, 
retaining  her  unbounded  wealth,  was  enabled  to  continue  that  influence  over  her  follow- 
ers, which  she  retains,  in  part,  to  this  day. 

535.  The  cornet  of  1680  would  have  been  still  more  alarming 
than  that  of  1456,  had  not  science  robbed  it  of  its  terrors,  and 
history  pointed  to  the  signal  failure  of  its  predecessor.  This 
comet  was  of  the  largest  size,  and  had  a  tail  whose  enormous 
length  was  more  than  ninety-six  millions  of  miles.  (Map  IX.. 
Fig.  75.) 

At  its  greatest  distance,  it  is  13,000,000,000  of  miles  from 
the  Sun  ;  and  at  its  nearest  approach,  only  574,000  miles  from 
his  center  ;*  or  about  130,000  miles  from  his  surface.  In  that 

*  In  Brewster's  edition  of  Ferguson,  this  distance  is  stated  as  only  49,000  miles.  This 
is  evidently  a  mistake ;  for  if  the  comet  approached  the  Sun's  center  within  49,000  miles, 
it  would  penetrate  390,000  miles  below  the  surface !  Taking  Ferguson's  own  elements  for 
computing  the  perihelion  distance,  the  result  will  be  494,460  miles.  The  mistake  may  be 
accounted  for,  by  supposing  that  the  cypher  had  been  omitted  in  the  copy,  and  the  period 
pointed  off  one  figure  farther  to  the  left.  Yet,  with  this  alteration,  it  would  be  still  incor- 
rect; because  the  Earth's  mean  distance  from  the  Sun,  which  is  the  integer  of  this  calcu- 
lation, is  assumed  at  82,000,000  of  miles.  The  ratio  of  the  comet's  perihelion  distance 
from  the  Sun,  to  the  Earth's  mean  distance,  as  given  by  M.  Pingre,  is  as  0.00603  to  1. 
This  multiplied  into  95,213,869,  gives  574,500  miles  for  the  comet's  perihelion  distance 
from  the  Sun's  center;  from  which,  if  we  substract  his  semi-diameter,  443,840  miles,  we 
shall  have  130,660  miles,  the  distance  of  the  comet  from  the  surface  of  the  Sun. 

Again,  if  we  divide  the  Earth's  mean  distance  from  the  Sun,  by  the  comet's  perihelion 
distance,  we  shall  find  that  the  latter  is  only  l-166th  part  of  the  Earth's  distance.  Now 
the  square  of  166  is  21,556 ;  and  this  expresses  the  number  of  times  that  the  Sun  appears 
larger  to  the  comet,  in  the  above  situation,  than  it  does  to  the  Earth.  Squire  makes  it 
8-1,596  times  larger. 

According  to  Newton,  the  velocity  is  880,000  miles  per  hour.  More  recent  discoveries 
indicate  a  velocity  of  1,240,108  miles  per  hour. 

Incidents  respecting  the  Turks  and  Church  of  Rome  ?  535.  Comet  of  1680  ?  Length  of 
ito  tail?  Aphelion  and  perihelion  distances?  Rapidity  of  its  motion  when  nearest  the  Sun? 
What  error  corrected ?  Appearance  of  the  Fun  from  that  point?  Heat  of  tbe  comet? 
Indicates  what?  Fanciful  theory  of  Dr.  Whiston,  and  remarks  upon  it? 


254  ASTRONOMY. 

part  of  its  orbit  which  is  nearest  the  Sun,  it  flies  with  the  amaz- 
ing swiftness  of  1,000,000  miles  in  an  hoar,  and  the  Sun,  as  seen 
from  it,  appears  27,000  times  larger  than  it  appears  to  us  ;  con- 
sequently, it  is  then  exposed  to  a  heat  27,000  times  greater  than 
the  solar  heat  at  the  Earth.  This  intensity  of  heat  exceeds, 
several  thousand  times,  that  of  red-hot  iron,  and  indeed  all  the 
degrees  of  heat  that  we  are  able  to  produce.  A  simple  mass  of 
vapor,  exposed  to  a  thousandth  part  of  such  a  heat,  would  be 
at  once  dissipated  in  space — a  pretty  strong  indication  that, 
however  volatile  are  the  elements  of  which  comets  are  composed, 
they  aro,  nevertheless,  capable  of  enduring  an  inconceivable 
intensity  of  both  heat  and  cold. 

This  <  the  comet  which,  according  to  the  reveries  of  Dr.  Whiston  and  others,  deluged 
the  wo- id  in  the  time  of  Noah.  Whiston  was  the  friend  and  successor  of  Newton  ;  but, 
anxjf-us  to  know  more  than  is  revealed,  he  passed  the  bounds  of  sober  philosophy,  and 
presumed  not  only  to  fix  the  residence  of  the  damned,  but  also  the  nature  of  their  punish- 
ment. According  to  this  theory,  a  comet  was  the  awful  prison-house  in  which,  as  it 
wheeled  from  the  remotest  regions  of  darkness  and  cold  into  the  very  vicinity  of  the 
?un,  hurrying  its  wretched  tenants  to  the  extremes  of  perishing  cold  and  devouring  fire, 
the  Almighty  was  to  dispense  the  severities  of  his  justice.  Such  theories  may  be  ingenious, 
but  they  have  no  basis  of  facts  to  rest  upon.  They  more  properly  belong  to  the  chimeras 
of  Astrology,  than  to  the  science  of  Astronomy. 

536.  When  we  are  told  by  philosophers  of  great  caution  and 
high  reputation,  that  "the  fiery  train  of  the  comet,  just  alluded 
to,  extended  from  the  horizon  to  the  zenith  ;  and  that  that  of 
1744  had,  at  one  time,  six  tails,  each  6,000,000  of  miles  long, 
long,  and  that  another,  which  appeared  soon  after,  had  one 
40,000,000  of  miles  long,  and  when  we  consider  also  the  incon- 
ceivable velocity  with  which  they  speed  their  flight  through  the 
solar  system,  we  may  cease  to  wonder  if,  in  the  darker  ages, 
they  have  been  regarded  as  evil  omens. 

But  these  idle  fantasies  are  not  peculiar  to  any  age  or  country.  Even  in  our  own 
times,  the  beautiful  comet  of  1811,  the  most  splendid  one  of  modern  times,  was  generally 
considered  among  the  superstitious,  as  the  dread  harbinger  of  the  war  which  was 
declared  in  the  following  spring.  It  is  well  known  that  an  indefinite  apprehension  of  a 
more  dreadful  catastrophe  lately  pervaded  both  continents,  in  anticipation  of  Biela's 
comet  of  1832. 

537.  The  nucleus  of  the  corneN  of  1811,  according  to  observa- 
tions made  near  Boston,  was  2617  miles  in  diamete*,  correspond- 
ing nearly  to  the  size  of  the  Moon.     The  brilliancy  with  which 
it  shone,  was  equal  to  one-tenth  of  that  of  the  Moon.     The 
envelope,   or  aeriform  covering  surrounding  the    nucleus,   was 
24,000  miles  thick,  about  five  hundred  times  as  thick  as  the 
atmosphere  which  encircles  the  Earth  ;  making  the  diameter  of 
comet,  including  its  envelope,   50,617   miles.      It  had  a  very 

530.  Why  not  strange  that  these  comets  were  regarded  as  evil  omens  ?  Are  such  super- 
stitions peculiar  to  any  age  or  country?  What  illustrations?  537.  Size  of  the  co:ne/. 
of  1S11?  Its  motion  at  its  perihelion  ? 


COMETS THEIR  NATURE,    MOTIONS,  ORBITS,  ETC.      255 

luminous  tail,  whose  greatest  length  was  one  hundred  millions  of 
miles.  Map  IX.,  Fig.  16.  This  comet  moved,  in  its  perihelion, 
with  an  almost  inconceivable  velocity — fifteen  hundred  times 
greater  than  that  of  a  ball  bursting  from  the  mouth  of  a  cannon. 

538.  According  to  Regiomontanus,  the  comet  of  1472  moved 
over  an  arc  of  120°  in  one  day.     Brydone  observed  a  comet  at 
Palermo  in  1770,  which  passed  through  50°  of  a  great  circle  in 
the  heavens  in  24  hours.     Another  comet,  which  appeared  in 
1759,  passed  over  41°  in  the  same  time.     The  conjecture  of  Dr. 
Halley,  therefore,  seems  highly  probable,  that  if  a  body  of  such  a 
size,  having  any  considerable  density,  and  moving  with  such  a 
velocity,  were  to  strike  our  Earth,  it  would  instantly  reduce  it 
to  chaos,  mingling  its  elements  in  ruin. 

The  transient  effect  of  a  body  passing  near  the  Earth,  could  scarcely  amount  to  any 
great  convulsion,  says  Dr.  Brewster  ;  but  if  the  Earth  were  actually  to  receive  a  shock 
from  one  of  these  bodies,  "  having  any  considerable  density,"  the  consequences  would 
indeed  be  awful.  A  new  direction  would  be  given  to  its  rotary  motion,  and  it  would 
revolve  around  a  new  axis.  The  seas,  forsaking  their  beds,  would  be  hurried,  by  their 
centrifugal  force,  to  the  new  equatorial  regions  ;  islands  and  continents,  the  abodes  of 
men  and  animals,  would  be  covered  by  the  universal  rush  of  the  waters  to  the  new 
equator,  and  every  vestige  of  human  industry  and  genius  would  be  at  once  destroyed. 
But  so  far  as  we  are  as  yet  acquainted  with  these  singular  bodies,  they  are  altogether  too 
light  and  gasseous  to  produce  any  such  results  by  collision. 

539.  The  chances  against  such  an  event,  however,  are  so  very 
numerous,  that  there  is  no  reason  to  dread  its  occurrence.     The 
French  government,  not  long  since,  called  the  attention  of  some 
of  her  ablest  mathematicians  and  astronomers  to  the'solution  of 
this  problem  ;  that  is,  to  determine  upon  mathematical  principles, 
how  many  chances  of  collision  the  Earth  was  exposed  to.     After  a 
mature  examination,  they  reported — "  We  have  found  that,  of 
281,000,000  of  chances,  there  is  only  one  unfavorable — there  ex- 
ists but  one  which  can  produce  a  collision  between  the  two  bodies." 

"Admitting,  then,"  say  they,  "  for  a  moment,  that  the  comets  which  may  strike  the 
Earth  with  their  nucleuses,  would  annihilate  the  whole  human  race;  the  danger  of  death 
to  each  individual,  resulting  from  the  appearance  of  an  unknown  c<mi?t,  would  be 
exactly  equal  to  the  risk  he  would  run,  if  in  an  urn  there  was  only  one  single  white  ball 
among  a  total  number  of  281,000,000  balls,  and  that  his  condemnation  to  death  would  be 
the  inevitable  consequence  of  the  white  ball  being  produced  at  the  first  drawing." 

A  little  reflection,  however,  will  show  that  all  such  fears  are  groundless.  The  same 
unerring  hand  that  guides  the  ponderous  planet  in  its  way,  directs  also  the  majestio 
comet ;  and  where  infinite  wisdom  and  almighty  power  direct,  it  is  almost  profane  to  talk 
of  collision  or  accident. 

540.  We  have  before  stated  that  comets,  unlike  the  planets, 
observe  no  one  direction  in  their  orbits,  but  approach  to,  and 
recede  from  their  great  center  of  attraction,  in  every  possible 

633.  Velocity  of  the  comet  of  1472?  Of  17TO?  Of  1759?  Dr.  Halley's  conjecture? 
Dr.  Brewster's?  Could  a  comet  produce  any  such  effects?  539.  Is  such  a  collision 
probable?  Why  not?  540.  What  said  of  the  orbits  of  comets  and  their  various 
directions  ? 


25t5  ASTRONOMY. 

direction.  Nothing  can  be  more  sublime,  or  better  calculated  to 
fill  the  mind  with  profound  astonishment,  than  to  contemplate  the 
revolution  of  comets,  while  in  that  part  of  their  orbits  which 
comes  within  the  sphere  of  the  telescope.  Some  seem  to  come 
up  from  the  immeasurable  depths  below  the  ecliptic,  and,  having 
doubled  the  heavens'  mighty  cape,  again  plunge  downward  with 
their  fiery  trains, 

"  On  the  long  travel  of  a  thousand  years." 

Others  appear  to  come  down  from  the  zenith  of  the  universe 
to  double  their  perihelion  about  the  Sun,  and  then  reascend  far 
above  all  human  vision.  Others  are  dashing  through  the  solar 
system  in  all  possible  directions,  and  apparently  without  any 
undisturbed  or  undisturbing  path  prescribed  by  Him  who  guides 
and  sustains  them  all. 

541.  Until  within  a  few  years,  it  was  universally  believed  that 
the  periods  of  their  revolutions  must  necessarily  .be  of  prodigious 
length  ;  but  within  a  few  years,  two  comets  have  been  discov- 
ered, whose   revolutions  are   performed,  comparatively,  within 
our  own  neighborhood.     To  distinguish   them  from  the  more 
remote,  they  are  denominated  the  Comets  of  a  short  period.     The 
first  was  discovered  in  the  constellation  Aquarius,  by  two  French 
astronomers,  in  the  year  1786.      The  same  comet  was  again 
observed  by  Miss  Caroline  Herschel,  in  the  constellation  Cygnus, 
in  1795,  and  again  in  1805.     In  1818,  Professor  Encke  deter- 
mined the  dimensions  of  its  orbit,  and  the  period  of  its  sidereal 
revolution  ;  for  which  reason  it  has  been  called  "  Encke 's  Comet. ' 
Map  IX.,  Fig.  77. 

This  comet  performs  its  revolution  around  the  Sun  in  about  3  years  and  4  months,  in 
an  elliptical  orbit  which  lies  wholly  within  the  orbit  of  Jupiter.  Its  mean  distance  from 
the  Sun  is  212,000,000  of  miles;  the  eccentricity  of  its  orbit  is  179,000,000  of  miles;  con- 
sequently, is  358,000,000  of  miles  nearer  the  Sun  in  its  perihelion,  than  it  is  in  its  aphe- 
lion. It  was  visible  throughout  the  United  States  in  1825,  when  it  presented  a  fine 
appearance.  It  was  also  observed  at  its  next  return  in  1828;  but  its  return  to  its  perihe- 
lion on  the  6th  of  May,  1832,  was  invisible  in  the  United  States,  on  account  of  its  great 
southern  declination.  It  has  returned  at  regular  periods  since  that  time. 

542.  The  second  "  comet  of  a  short  period,"  was  observed  in 
1772  ;  and  was  seen  again  in  1805.     It  was  not  until  its  reap- 
pearance in  1826,  that  astronomers  were  able  to  determine  the 
elements  of  its  orbit,  and  the  exact  period   of  its  revolution. 
This  was  successfully  accomplished  by  M.  Biela  of  Josephstadt ; 
hence  it  is  called  Bidajs  Comet, 

541.  What  opinion  respecting  their  periods?  What  distinction  in  comets  founded  on 
the  .engths  of  their  periods?  History  of  u Encke1  s  Comet?"  Its  period,  orbit,  mean 
iV.ance,  eccentricity  of  its  orbit?  542.  History  of  " Bitla 'a  Cometf"  Its  diameter V 


COMETS THEIR    NATURE,    MOTIONS,    ORBITS,    ETC.     257 

According  to  observations  made  upon  it  in  1805,  by  the  celebrated  Dr.  Olbers,  its 
diameter,  including  its  envelope,  is  42,280  miles.  It  is  a  curious  fact,  that  the  path  of 
Jiiela's  Comet  passes  very  near  to  that  of  the  Earth ;  so  near,  that  at  the  moment  the 
center  of  the  comet  is  at  the  point  nearest  to  the  Earth's  path,  the  matter  of  the  comet 
extends  beyond  that  path,  and  includes  a  portion  within  it.  Thus,  if  the  Earth  were  a4 
that  point  of  its  orbit  which  is  nearest  to  the  path  of  the  comet,  at  the  same  moment 
that  the  comet  should  be  at  that  point  of  its  orbit  which  is  nearest  to  the  path  of  tho 
Earth,  the  Earth  would  be  enveloped  in  the  nebulous  atmosphere  of  the  comet. 

With  respect  to  the  effect  which  might  be  produced  upon  our  atmosphere  by  such  a 
circumstance,  it  is  impossible  to  offer  anything  but  the  most  vague  conjecture.  Sir  John 
Herschel  was  able  to  distinguish  stars  as  minute  as  the  16th  or  17th  magnitude  through 
th&  l^ody  of  the  comet  1  Hence  it  seems  reasonable  to  infer,  that  the  nebulous  matter  of 
which  it  is  composed,  must  be  infinitely  more  attenuated  than  our  atmosphere  ;  so  that 
for  every  particle  of  cometary  matter  which  we  should  inhale,  we  should  inspire  millions 
of  particles  of  atmospheric  air. 

543  This  is  one  of  the  comets  that  was  to  come  into  collision 
with  the  Earth,  and  to  blot  it  out  from  the  Solar  System.  In 
returning  to  its  perihelion,  November  26th,  1832,  it  was  comput- 
ed that  it  would  cross  the  Earth's  orbit  at  a  distance  of  only 
18,500  miles.  It  is  evident  that  if  the  Earth  had  been  in  that 
part  of  her  orbit  at  the  same  time  with  the  comet,  our  atmos- 
phere would  have  mingled  with  the  atmosphere  of  the  comet, 
and  the  two  bodies,  perhaps,  have  come  in  contact.  But  the 
comet  passed  the  Earth's  orbit  on  the  29th  of  October,  in  the 
8th  degree  of  Sagittarius,  and  the  Earth  did  not  arrive  at  that 
point  un+il  the  30th  of  November,  which  was  32  days  after- 
wards. 

If  we  multiply  the  number  of  hours  in  32  days,  by  68,000  (the  velocity  of  the  Earth  pel 
hour),  we  shall  find  that  the  Earth  was  more  than  52,000,000  miles  behind  the  comet  when 
it  crossed  her  orbit.  Its  nearest  approach  to  the  Earth  at  any  time,  was  about  51,000,000 
of  miles  ;  its  nearest  approach  to  the  Sun,  was  about  83,000,000  of  miles.  Its  mean  dis- 
tance from  the  Sun,  or  half  the  longest  axis  of  its  orbit,  is  387,000,000  of  miles.  Its 
eccentricity  is  253,000,000  of  miles  ;  consequently,  it  is  507,000,000  of  miles  nearer  the 
Sun  in  its  perihelion  than  it  is  in  its  aphelion.  The  period  of  its  sidereal  revolution  is 
2460  days,  or  about  6%  days. 

544.  Although  the  comets  of  Encke  and  Biela  are  objects  of 
very  great  interest,  yet  their  short  periods,  the  limited  space 
within  which  their  motion  is  circumscribed,  and  consequently  the 
very  slight  disturbance  which  they  sustain  from  the  attraction 
of  the  planets,  render  them  of  less  interest  to  physical  astrono- 
my thar  those  of  longer  periods.  They  do  not,  like  them,  rush 
from  the  invisible  and  inaccessible  depths  of  space,  and,  after 
sweepirg  our  system,  depart  to  distances  with  the  conception  of 
which  the  imagination  itself  is  confounded.  They  possess  none 
of  that  grandeur  which  is  connected  with  whatever  appears  to 
break  through  the  fixed  order  of  the  universe. 

What  curious  fact  stated ?  What  result  if  the  Earth  were  to  be  enveloped  in  the  comet? 
543.  What  mischief  formerly  anticipated  from  Biela's  comet?  Its  return  in  1882  V  How 
near  a  collision  in  distance  and  in  time?  Its  nearest  approach  to  the  Earth  ?  To  the 
Sun?  Its  mean  distance  from  him?  Its  eccentricity  and  period?  54-1.  Why  are  the 
c'.iuKs  of  short  periods  less  interesting  than  others  ?  For  what  comet  is  it  reserved  to 
9<*v.>- 1  grounds  for  the  proudest  triumph?  of  mathtuiatical  science? 


258  ASTRONOMY. 

It  is  reserved  for  the  comet  of  Halley  alone  to  afford  the  proudest  triumphs  to  thowi 
powers  of  calculation  by  which  we  are  enabled  to  follow  it  in  the  depths  of  space, 
§,000,000,000  of  miles  beyond  the  extreme  verge  of  the  solar  system;  and,  notwithstand- 
ing the  disturbances  which  render  each  succeeding  period  of  its  return  different  from 
the  last,  to  foretell  that  return  with  precision.  To  be  able  to  predict  the  very  day  and 
circumstances  of  the  return  of  such  a  bodiless  and  eccentric  wanderer,  after  the  lapse 
of  so  many  years,  evinces  a  perfection  of  the  astronomical  calculus  that  may  justly 
challenge  our  admiration. 

545.  "The  re-appearance  of   Biela's  comet,"  says  Herschel, 
"  whose  return  in  1832  was  made  the  subject  of  elaborate  cal- 
culations by  mathematicians  of  the  first  eminence,  did  not  disap- 
point the  expectations  of  astronomers.     It  is  hardly  possible  to 
imagine  anything  more  striking  than  the  appearance,  after  the 
lapse  of  nearly  seven  years,  of  such  an  all  but  imperceptible 
cloud  or  wisp  of  vapor,  true,  however,  to  its  predicted  sime,  and 
place,  and  obeying  laws  like  those  which  regulate  the  planets." 

Herschel,  whose  Observatory  was  at  Slough,  England,  observed  the  daily  progress  of 
this  comet  from  the  24th  of  September,  until  its  disappearance,  compared  its  actual  posi- 
tion from  day  to  day,  with  its  calculated  position,  and  found  them  to  agree  within  four 
or  five  minutes  of  time  in  right  ascension,  and  within  a  few  seconds  of  declination. 
Its  position,  then,  as  represented  on  a  planisphere  wnich  the  author  prepared  for  his 
pupils,  and  afterwards  published,  was  true  to  within  a  less  space  than  one-third  of  its 
projected  diameter.  Like  some  others  that  have  been  observed,  this  comet  has  no  lumi- 
nous train  by  which  it  can  be  easily  recognized  by  the  naked  eye,  except  when  it  is  very 
near  the  Sun.  This  is  the  reason  why  it  was  not  more  generally  observed  at  its  late 
return. 

Although  this  comet  is  usually  denominated  "Biela's  comet,"  yet  it  seems  that 
M.  Gambart,  director  of  the  Observatory  at  Marseilles,  is  equally  entitled  to  the  honor  of 
identifying  it  with  the  comet  of  1772,  and  of  1805.  He  discovered  it  only  10  days  after 
Biela,  and  immediately  set  about  calculating  its  elements  from  his  own  observations,  which 
are  thought  to  equal,  if  they  do  not  surpass,  in  point  of  accuracy,  those  of  every  other 
astronomer. 

546.  Up  to  the  beginning  of  the   17th  century,  HO  correct 
notions  had  been  entertained  in  respect  to  the  paths  of  comets. 
Kepler's  first  conjecture  was  that  they  moved  in  straight  lines  ; 
but  as  that  did  not  agree  with  observation,  he  next  concluded 
that  they  were  parabolic  curves,  having  the  Sun  near  the  vertex, 
and  running  indefinitely  into  the  regions  of  space  at  both  extre- 
mities.    There  was  nothing  in  the  observations  of  the  earlier 
astronomers  to  fix  their  identity,  or  to  lead  him  to  suspect  that 
any  one  of  them  had  ever  been  seen  before  ;  much  less  that  they 
formed  a  part  of  the  solar  system,  revolving  about  the  Sun  in 
elliptical  orbits  that  returned  into  themselves. 

547.  This  grand  discovery  was  reserved  for  one  of  the  most 
industrious  and  sagacious  astronomers  that  ever  lived — this  was 
Dr.  Halley,  the  cotemporary  and  friend  of  Newton.     When  the 
comet  of  1682  made  its  appearance,  he  set  himself  about  observ- 
ing it  with  great  care,  and  found  there  was  a  wonderful  resera- 

545.  Remarks  on  the  re-appearance  of  Biela's  comet?     What  remarkabl-    calculation 
referred  to?     Form  of  this  comet?     Is  it  really  Biela's  comet?        54C.  Former  kncw- 
f  the  orbits  of  comets?        547.  What  .. _^u  discovery,  and  by  whom9    Process 


CC-METS THEIR  NATURE,  MOTIONS,  ORBITS,    ETC         259 

blance  between  it  and  three  other  comets  that  he  found  recorded, 
the  comets  of  1456,  of  1531,  and  1607.  The  times  of  their 
appearance  had  been  nearly  at  equal  and  regular  intervals  ;  their 
perihelion  distances  were  nearly  the  same  ;  and  he  finally  proved 
them  to  be  one  and  the  same  comet,  performing  its  circuit  around 
the  Sun  in  a  period  varying  a  little  from  76  years.  It  is,  there- 
fore, called  Halky's  comet.  (Map  IX.,  Fig.  78.) 

The  orbit  of  Halley's  comet  extends  outward  about  120,000,000 
of  miles  beyond  the  orbit  of  Neptune,  as  represented  in  the  fol 
lowing  cut  : 


ORBIT  OF  HALLKT'S  COMET. 


This  is  the  same  comet  that  filled  the  eastern  world  with  so  much  consternation  in  1456, 
as  stated  on  page  253,  and  became  an  object  of  such  abhorrence  to  the  Church  of  Rome. 

The  periodic  times  of  the  three  comets  just  described,  are  as 
follow : ' 

Encke's,  1212  days. 
Biela's,  2461  days. 
Halley's,  28,000  days. 

Halley's  comet,  true  to  its  predicted  time  and  place,  is  now  (Oct.  1835)  visible  in  the 
evening  sky.  But  we  behold  none  of  those  phenomena  which  threw  our  ancestors  of  the 
middle  ages  into  agonies  of  superstitious  terror.  We  see  not  the  cometa  JiorrendoB 
magnitudinis,  as  it  appeared  in  1305,  nor  that  tail  of  enormous  length  which,  in  1456, 
extended  over  two-thirds  of  the  interval  between  the  horizon  and  the  zenith,  nor  even  a 
star  as  brilliant  as  was  the  same  comet  in  1682,  with  its  tail  of  30*. 

Its  mean  distance  from  the  Sun  is  1,713,700,000  miles;  the  eccentricity  of  its  orbit  is 
1,658,000,000  miles;  consequently  it  is  3,316,000,000  miles  farther  from  the  Sun  in  its 
aphelion  than  it  is  in  its  perihelion.  In  the  latter  case  its  distance  from  the  sun  is  only 
55,700,000  miles ;  but  in  the  former  it  is  3,371,700,000  miles.  Therefore,  thpugh  its  aphe- 
lion distance  be  great,  its  mean  distance  is  less  than  that  of  Uranus  ;  and  great  as  is  the 
aphelion  distance,  it  is  but  a  very  small  fraction  less  than  &n.e-Jive  thousandth  part  of 
that  distance  from  the  Sun,  beyond  which  the  very  nearest  of  the  fixed  stars  must  be 
situated ;  and,  as  the  determination  of  their  distance  is  negative  and  not  positive,  the 
nearest  of  them  may  be  at  twice  or  ten  times  that  distance. 

of  the  discovery?  Aphelion  distance  of  Halley's  comet?  What  former  visit  to  our  sys- 
tem referred  to  ?  Periods  of  the  three  comets  just  described  ?  Appearance  of  Halley's 
comet  in  1835?  Its  mean  distance  from  the  Sun?  How  compare  with  that  of  Uranui  t 
Hov  does  his  greatest  distance  compare  with  that  of  the  Fixed  Stars? 


260  ASTRONOMY. 

548.   The    Orbit    of    Encke's  OBBrra  or  SBVEBAL  OOM*TB 

comet  is  wholly  within  the  orbit 
of  Jupiter,  while  that  of  Biela's 
extends  but  a  short  distance 
beyond  it.  The  aphelion  dis- 
tance  of  Halley's  comet  is 
3,400,000,000  of  miles,  or 
050,000,000  of  miles  beyond 
the  orbit  of  Neptune.  Aiid 
even  this  is,  in  reality,  a  comet 
of  short  period  compared  with 
many  that  belong  to  our  sys- 
tem. 

549.  The  comet  of  1819  wasre-  -""  "^:- 
markable  for  its  straight  wedge- 
shaped  appearance — not  altogether  unlike  a  shuttle-cock.  It 
exhibited  none  of  that  curvature  in  its  form  which  is  an  almost 
universal  characteristic  of  cometary  bodies.  Map  IX.,  Fig.  79. 

550.  The  comet  of  1843  was  one  of  the  most  magnificent  of 
modern  times  (See  Map  IX.,  Fig.  80).     It  was  more  than  60° 
in  length.     In  the  Southern  Hemisphere  it  was  so  brilliant  as 
to  throw  a  very  strong  light  upon  the  Earth.     As  its  distance 
from  the  Sun  varied,  its  color  varied,  from  pale  orange  to  "rose 
red,"  and  then  to  white.     "  It  passed  its  perihelion  on  the  27th 
of  February,  at  which  time  it  almost  grazed  the  surface  of  the 
Sun,   approaching   nearer   to   that   luminary   than   any  comet 
hitherto  observed.     Its  motions  at  this  time  were  astonishingly 
swift,  and  its  brilliancy  such  as  to  induce  the  belief  that  it  was  at 
a  white  heat  through  its  whole  extent.     Its  period  is  supposed 
to  be  21-J-  years  ;  consequently  this  must  be  its  eighth  return 
since  1668  ;  and  it  will  visit  our  sphere  again  in  1865." 

At  the  time  of  the  appearance  of  this  comet,  Rev.  Mr.  Miller  and  others  were  earnestly 
warning  the  people  of  the  United  States,  that  the  world  was  to  be  burned  up  on  the  28<i 
of  April  following ;  and  the  appearance  cf  the  comet  was  regarded  by  many  as  an  indica- 
tion that  the  end  of  all  things  was  at  hand. 

551.  The  number  of  comets  which  have  been  observed  since 
the  Christian  era,  amounts  to  650.     Scarcely  a  year  has  passed 
without  the  observation  of  one  or  two.     And  since  multitudes 
of  them  must  escape  observation,  by  reason  of  their  traversing 
that  part  of  the  heavens  which  is  above  the  horizon  in  the  day 

548.  Where  are  the  orbits  of  Encke's  and  Biela's  comets  situated?  What  said  of  Ral- 
ly's comet?  549.  Comet  of  1819?  550.  That  of  1S43?  Its  length?  Brilliancy? 
What  variation  in  its  color  ?  Its  perihelion  passage  ?  Heat  ?  Its  period  ?  Next  appear- 
ance? Incident  of  its  last  appearance?  551.  Number  of  comets?  Why  so  few  sefn? 


COMETS THEIR    NA1 URE,   MOTIONS,  ORBITS,    ETC.       261 

time,  their  whole  number  is  probably  many  thousands.  Comets 
so  circumstanced,  can  only  become  visible  by  the  rare  coinci- 
dence of  a  total  eclipse  of  the  Sun — a  coincidence  which  hap- 
pened, as  related  by  Seneca,  60  years  before  Christ,  wlen  a 
large  comet  was  actually  observed  very  near  the  Sun. 

But  M.  Arago  reasons  in  the  following  manner,  with  respect  to  the  number  of  comets  : — 
The  number  of  ascertained  comets,  which,  at  their  least  distances,  pass  within  the  orbit 
of  Mercury,  is  thirty.  Assuming  that  the  comets  are  uniformly  distributed  throughout 
the  solar  system,  there  will  be  117,649  times  as  many  comets  included  within  the  orbit  of 
Uranus,  as  there  are  within  the  orbit  of  Mercury.  But  as  there  are  30  within  the  orbit 
of  Mercury,  there  must  be  3,529,470  within  the  orbit  of  Uranus  ! 

552.  Of  97  comets  whose  elements  have  been  calculated  by 
astronomers,  24  passed  between  the  Sun  and  the  orbit  of  Mer- 
cury: 33  between  the  orbits  of  Mercury  and  Venus  ;  21  between 
the  orbits  of  Venus  and  the  Earth;  15  between  the  orbits  of 
Ceres  and  Jupiter.     49  of  these  comets  move  from  east  to  west, 
and  49  in  the  opposite  direction.     The  total  number  of  distinct 
comets,  whose  paths  during  the  visible  part  of  their  course  had 
been  ascertained,  up  to  the  year  1855,  was  about  one  hundred 
and  fifty. 

553.  What  regions  these  bodies  visit,  when  they  pass  beyond 
the  limits  of  our  view  ;  upon  what  errands  they  come,  when 
they  again  revisit  the  central  parts  of  our  .system  ;  what  is  the 
difference  between  their  physical  constitution  and  that  of  the 
Sun  and  planets  ;  and  what  important  ends  they  are  destined 
to  accomplish  in  the    economy  of  the  Universe,  are  inquiries 
which  naturally  arise  in  the  mind,  but  which  surpass  the  limited 
powers  of  the  human  understanding  at  present  to  determine. 

554.  Such  is  the  celestial  system  with  which  our  Earth  was 
associated  at  its  creation,  distinct  from  the  rest  of  the  starry 
hosts.     Whatever   may  be  the   comparative  antiquity  of  our 
globe,  and  the  myriads  of  radiant  bodies  which  nightly  gem  the 
immense  vault  above  us,  it  is  most  reasonable  to  conclude,  that 
the  Sun,  Earth,  and  planets  differ  little  in  the  date  of  their 
origin.     This,  fact,  at  least,  seems  to  be  philosophically  certain, 
that  all  the  bodies  which  compose  our  solar  system  must  have 
been  placed  at  one  and  the  same  time  in  that  arrangement,  and 
in  those  positions  in  which  we  now  behold  them  ;  because  all 
maintain  their  present  stations,  and  motions,  and  distances,  by 
their  mutual  action  on  each  other.     Neither  could  it  be  where  it 

Phenomenon  60  years  before  Christ?  M.  Arago's  reasoning  and  conclusion?  552. 
Perihelion  distances  of  various  comets  ?  Directions  in  longitude  ?  Number  whose  paths 
have  been  ascertained?  553.  What  inquiries  awakened  by  the  visits  of  cometary 
bodies?  5iJ4.  Remarks  respecting  the  date  of  the  sola*  system?  What  supposed  p/oof 
that  the  whole  system  was  created  at  oucc? 


262  ASTRONOMY. 

is,  nor  move  as  it  does,  nor  appear  as  we  see  it,  unless  they 
were  all  co-existent.  The  presence  of  each  is  essential  to  the 
system — the  Sun  to  them,  they  to  the  Sun,  and  all  to  each 
other.  This  fact  is  a  strong  indication  that  their  formation  waa 
simultaneous. 


CHAPTER  X. 

OF    THE    FORCES    BY   WHICH    THE    PLANETS    ARE 
RETAINED   IN   THEIR    ORBITS. 

555.  HAVING  described  the  real  and  apparent  motions  of  tha 
bodies  which  compose  the  solar  system,  it  may  be  interesting 
next  to  show,  that  these  motions,  however  varied  or  complex 
they  may  seem,  all  result  from  one  simple  principle,  or  law, 
namely,  the 

LAW    OF   UNIVERSAL   GRAVITATION. 

By  gravitation  is  meant,  that  universal  law  of  attraction,  by 
which  every  particle  of  matter  in  the  system  has  a  tendency  to 
every  other  particle.  This  attraction,  or  tendency  of  bodies 
towards  each  other,  is  in  proportion  to  the  quantity  of  matter 
they  contain.  The  Earth,  being  immensely  large  in  "comparison 
with  all  other  substances  in  its  vicinity,  destroys  the  effect  of 
this  attraction  between  smaller  bodies,  by  bringing  them  all  to 
itself. 

It  is  said,  that  Sir  Isaac  Newton,  when  he  was  drawing  to  a  close  the  demonstration  ol 
the  great  truth,  that  gravity  is  the  cause  which  keeps  the  heavenly  bodies  in  their  orbits, 
was  so  much  agitated  with  the  magnitude  and  importance  of  the  discovery  he  was  about 
to  make,  that  he  was  unable  to  proceed,  and  desired  a  friend  to  finish  what  the  intensity 
of  his  feelings  did  not  allow  him  to  do. 

556.  The  attraction  of  gravitation  is  reciprocal.     All  bodies 
not  only  attract  other  bodies,  but  are  themselves  attracted,  and 
both  according  to  their  respective  quantities  of  matter.     The 
Sun,  the  largest  body  in  our  system,  attracts  the  Earth  and  all 
the  other  planets,  while  they  in  turn  attract  the  Sun.     The 

555.  Subject  of  this  chapter?  What  is  meant  by  gravitation  ?  Upon  what  does  the 
amount  of  this  attraction  depend?  Influence  of  the  Earth?  Anecdote  of  Newton? 
N56.  Is  attraction  reciprocal?  What  illustration  cited?  Ways  in  which  attra<  tiou 


LAW    OF    GRAVITATION.  263 

Earth,  also,  attracts  the, .Moon,  and  she  in  tnrn  attracts  the 
Earth.  A  ball,  thrown  upwards  from  the  Earth,  is  brought 
again  to  its  surface  ;  the  Earth's  attraction  not  only  counter 
balancing  that  of  the  ball,  but  also  producing  a  motion  of  the 
ball  towards  itself. 

This  disposition,  or  tendency  towards  the  Earth,  is  manifested  in  whatever  falls,  whether 
it  be  a  pebble  from  the  hand,  an  apple  from  a  tree,  or  an  avalanche  from  a  mountain. 
All  terresual  bodies,  not  excepting  the  waters  of  the  ocean,  gravitate  towards  the  center 
of  the  Earth,  and  it  is  by  the  same  power  that  animals  on  all  parts  of  the  globe  stand 
with  their  feet  pointing  to  its  center. 

557.  The  power  of  terrestial  gravitation  is  greatest  at  the 
Earth's  surface,  whence  it  decreases  both  upwards  and  down- 
wards ;  but  not  both  ways  in  the  same  proportion.     It  decreases 
upwards  as  the  square  of  the  distance,  from  the  Earth's  center 
increases  ;  so  that  at  a  distance  from  the  center  equal  to  twice 
the  semi-diameter  of  the  Earth,  the  gravitating  force  would  be 
only  one-fourth  of  what  it  is  at  the  surface.     But  below  the  sur- 
face, it  decreases  in  the  direct  ratio  of  the  distance  from  the 
center  ;  so  that  at  a  distance  of  half  a  semi-diameter  from  the 
center,  the  gravitating  force  is  but  half  of  what  it  is  at  the 
surface. 

Weight  and  Gravity,  in  this  case,  are  synonymous  terms.  We  say  a  piece  of  lead 
weighs  a  pound,  or  16  ounces ;  but  if  by  any  means  it  could  be  raised  4000  miles  abovo 
the  surface  of  the  Earth,  which  is  about  the  distance  of  the  surface  from  the  center,  and 
consequently  equal  to  two  semi-diameters  of  the  Earth  above  its  center,  it  would  weigh 
only  one-fourth  of  a  pound,  or  four  ounces ;  and  if  the  same  weight  could  be  raised  to  an 
elevation  of  12,000  miles  above  the  surface,  or  four  semi-diameters  above  the  center  of 
the  Earth,  it  would  there  weigh  only  one-sixteenth  of  a  pound,  or  one  ounce. 

558.  The  same  body,  at  the  center  of  the  Earth,  being  equally 
attracted  in  every  direction,  would  be  without  weight  ;  at  1000 
miles  from  the  center  it  would  weigh  one-fourth  of  a  pound  :  at 
2000  miles,  one-half  of  a  pound  ;  at  300€  miles,  three-fourths  of 
a  pound  ;  and  at  4000  miles,  or  at  the  surface,  one  pound. 

It  is  a  universal  law  of  attraction,  that  its  power  decreases  as 
the  square  of  the  distance  increases.  The  converse  of  this  is  also 
true,  viz.:  The  power  increases  as  the  square  of  the  distance 
decreases.  Giving  to  this  law  the  form  of  a  practical  rule,  it  will 
stand  thus  : 

The  gravity  of  bodies  above  the  surface  of  the  Earth  decreases 
in  a  duplicate  ratio  (or  as  the  squares  of  their  distances),  in  semi- 
diameters  of  the  Earth,  from  the  Earths  center.  That  is,  when 

manifests  itself?  55T.  Where  is  the  power  of  terrestrial  gravitation  greatest?  How 
iiminished  ?  In  what  ratio  as  we  ascend  above  the  Earth  ?  As  we  descend  toward  its 
Center?  Are  weight  and  gravity  the  same  ?  568.  What  would  be  the  weight  of  a  body 
at  the  Earth's  center?  At  100  miles  from  th<?  center  ?  At  2000  miles  ?  At  4000?  What 
universal  iw?  What  rule  based  upon  this  law?  What  illustrations  given?  What  ruU 


ASTRONOMY. 

the  gravity  is  increasing,  multiply  the  weight  by  the  square  of 
the  distance  ;  but  when  the  gravity  is  decreasing,  divide,  the 
weight  by  the  square  of  the  distance. 

Suppose  a  body  weighs  40  pounds  at  2000  miles  above  the  Earth's  surface,  what  would 
It  weigh  at  the  surface,  estimating  the  Earth's  semi-diameter  at  4000  miles.  From  tho 
center  to  the  given  height,  is  1J$  semi-diameters;  the  square  of  l>$,or  1.5  is  2.25,  which, 
multiplied  into  the  weight  (40),  gives  90  pounds,  the  answer. 

Suppose  a  body  which  weighs  256  pounds  upon  the  surface  of  the  Earth,  be  j-aised  to 
the  distance  of  the  Moon  (240,000  miles),  what  would  be  its  weight?  Thus,  4000)240,000(60 
semi-diameters,  the  square  of  which  is  3600.  As  the  gravity  in  this  case  is  decreasing, 
divide  the  weight  by  the  square  of  the  distance,  and  it  will  give  3600)256(1- 16th  of  a 
pound, or  1  ounce. 

To  find  to  what  height  a  given  weight  must  be  raised  to  lose  a  certain  portion  of  its 
weight. 

RULE. — Divide  the  weight  at  the  surface  by  the  required  weight,  and  extract  the 
square  root  of  the  quotient.  Ex.  A  boy  weighs  100  pounds,  how  high  must  he  be  carried 
to  weigh  but  4  pounds?  Thus,  100  divided  by  4,  gives  25,  the  square  root  of  which  is  5 
semi-diameters,  or  20,000  miles  above  the  center. 

559.  Bodies  of  equal  magnitude  do  not  always  contain  equal 
quantities  of  matter  ;  a  ball  of  cork,  of  equal  bulk  with  one  of 
lead,  contains  less  matter,  because  it  is  more  porous.  The  Sun, 
though  fourteen  hundred  thousand  times  larger  than  the  Earth, 
being  much  less  dense,  contains  a  quantity  of  matter  only 
355,000  as  great,  and  hence  can  exert  an  attractive  iorce  only 
355,000  times  greater  than  that  which  the  Earth  is  capable  of 
exerting. 

The  quantity  of  matter  in  the  Sun  is  780  time?  greater  than  that  of  all  the  plunets  and 
satellites  belonging  to  the  Solar  System  ;  consequently,  their  whole  united  force  of  attrac- 
tion is  780  times  less  upon  the  Sun,  than  that  of  the  Sun  upon  them. 

CENTER   O?   GRAVITY. 


560.  The  Center  of  Gravity  of  a  body,  is  that  point  in  which 
its  whole  weight  is  concentrated,  and  upon  which  it  would  rest, 
if  freely  suspended.  If  two  weights,  one  of  ten  pounds,  the 
other  of  one  pound,  be  connected  together  by  a  rod  eleven  feet 
long,  nicely  poised  on  a  center,  and  then  be  thrown  into  a  free 
rotary  motion,  the  heaviest  will  move  in  a  circle  with  a  radius  of 
one  foot,  and  the  lightest  will  describe  a  circle  with  a  radius  of 
ten  feet ;  the  center  around  which  they  move  is  their  common 
center  of  gravity.  (See  the  Figure.) 

to  find  what  height  a  given  weight  must  be  raised  to  lose  a  certain  portion  of  ita 
weight?  55S).  Do  bodies  attract  in  proptn-tion.  to  their  bulk?  Why  not?  What  illua- 
IrfttkMU?  '(uantity  of  matter  in  the  Sun?  6f>0.  What  is  meant  by  the  center  cf 
gravity  f  Illuairuiiuii?  ilow  with  the  Hun  and  pUuets?  lluir  would  n  be  it  ;h«ro  w.u? 


ATTRACTIVE    AND    PROJECTILE    FORCES.  205 

Tims  the  Sun  and  planets  move  around  in  an  imaginary  point 
as  a  center,  always  preserving  an  equilibrium. 

If  there  were  but  one  body  in  the  universe,  provided  it  were  of  uniform  density,  th< 
nenter  of  it  would  be  the  center  of  gravity  towards  which  all  the  surrounding  portions 
would  uniformly  tend,  and  they  would  thereby  balance  each  other.  Thus  the  center  of 
gravity,  and  the  body  itself,  would  for  ever  remain  at  rest.  It  would  neither  move  up  nor 
down ;  there  being  no  other  body  to  draw  it  in  any  direction.  In  this  case,  the  terms  up 
aid  down  would  have  no  meaning,  except  as  applied  to  the  body  itself,  to  express  the 
direction  of  the  surface  from  the  center. 

561.  Were  the  Earth  the  only  body  revolving  about  the  Sun, 
as  the  Suu's  quantity  of  matter  is   355,000   times  as  great  as 
that  of  the  Earth,  the  Sun  would  revolve  in  a  circle  equal  onh 
to  the  three  hundred  and  fifty-five  thousandth  part  of  the  Earth's 
distance  from  it  ;  but  as  the  planets  in  their  several  orbits  vary 
their  positions,  the  center  of  gravity  is  not  always  at  the  same 
distance  from  the  Sun. 

The  quantity  of  matter  in  the  Sun  so  far  exceeds  that  of  all 
the  planets  together,  that  were  they  all  on  one  side  of  him,  he 
would  never  be  more  than  his  own  diameter  from  the  common 
center  of  gravity  ;  the  Sun  is,  therefore,  justly  considered  as  the 
center  of  the  system. 

562.  The  quantity  of  matter  in  the  Earth  being  about  80 
times  as  great  as  that  of  the  Moon,  their  common  center  of 
gravity  is  80  times  nearer  the  former  than  the  latter,  which  is 
about  3000  miles  from  the  Earth's  center.  The  secondary  planets 
are  governed  by  the  same  laws  as  their  primaries,  and  both 
together  movo  around  a  common  center  of  gravity.     Ev^ry  sys- 
tem in  the  universe  is  supposed  to  revolve  in  like  manner,  around 
one  common  center. 

ATTRACTIVE    AND    PROJECTILE    FORCES. 

563.  All  simple  motion  is  naturally  rectilinear  ;  that  is,  all 
bodies  put  in  motion  would  continue  to  go  forward  in  straight 
lines,  as  long  -as  they  met  with  no  resistance  or  diverting  force. 
On  the  other  hand,  the  Sun,  from  his  immense  size,  would,  by 
the   power  of  attraction,  draw  all  the   planets  to  nim,  if  his 
attractive  force  were  not  counterbalanced  by  the  primitive  im- 
pulse of  the  planetary  bodies  to  move  in  straight  lines. 

564.  The  attractive  power  of  a  body  drawing  another  body 

but  one  body  in  the  universe?  561.  Suppose  the  Earth  was  the  only  body  revolving 
around  the  Sun?  Is  the  center  of  gravity  always  at  the  same  distance  from  the  Sun? 
Why  not  ?  How  would  it  be  if  all  the  planets  were  on  one  side  of  him?  562.  What  is 
the  amount  of  matter  in  the  Earth  as  compared  with  the  Moon?  How  with  the  second- 
ary planets?  With  other  systems  in  the  universe?  563.  What  is  the  chaiacter  of  all 
9>mi>le  motion?  What  illustrations  given  ?  664  What  is  the  attractive  power  called ? 


2(36  ASTRONOMY. 

towards  the  center,  is  denominated  Centripetal  force  ;  and  the  ten* 
dency  of  a  revolving  body  to  fly  from  the  center  in  a  tangent 
line,  is  called  the  Projectile  or  Centrifugal  force.  The  joint 
action  of  these  two  central  forces  gives  the  planets  a  circular 
motion,  and  retains  them  in  their  orbits  as  they  revolve,  the  pri- 
maries about  the  Sun,  and  the  secondaries  about  their  primaries. 
565.  The  degree  of  the  Sun's  attractive  power  at  each  par* 
tictflar  planet,  whatever  be  its  distance,  is  uniformly  equal  to 
the  centrifugal  force  of  the  planet.  The  nearer  any  plane c  is  to 
the  Sun,  the  more  strongly  is  it  attracted  by  him  ;  the  farther 
any  planet  is'  from  the  Sun,  the  less  is  it  attracted  by  him  ; 
therefore,  those  planets  which  are  the  nearer  to  the  Sun,  must 
move  the  faster  in  their  orbits,  in  order  thereby  to  acquire  cen- 
trifugal forces  equal  to  the  power  of  the  Sun's  attraction  ;  and 
those  which  are  the  farther  from  the  Sun,  must  move  the  slower, 
in  order  that  they  may  not  have  too  great  a  degree  of  centri- 
fugal force,  for  the  weaker  attraction  of  the  Sun  at  those 
distances. 

LAWS    OF    PLANETARY   MOTION. 

566  Three  very  important  laws,  governing  the  movements  of 
the  planets,  were  discovered  by  Kepler,  a  German  astronomer, 
in  1609  In  honor  of  their  discoverer,  they  are  called  Kepler' a 
Laws.  Kepler  was  a  disciple  of  Tycho  Brake,  a  noted  astrono 
mer  of  Denmark,  and  was  equally  celebrated 

.    11*  -i  TT  •  •  -\  -»  APHELION* 

with  his  renowned  tutor.     His  residence  and  ...-•»— .x 

observatory  were   at  Wirtemburgh,   in   Ger- 
many. 

The  first  of  these  laws  is,  that  the  orbits  of 
nil  the,  planets  are  elliptical,  having  the  Sun  in 
the  common  focus. 

The  point  in  a  planet's  orbit  nearest  the  Sun  is  called  the 
perihelion  point,  and  the  point  most  remote  the  aphelion  point. 
Perihelion  is  from  peri,  about  or  near,  and  fielios,  the  Sun ;  and 
aphelion,  from  apo,  from,  and  helio»t  the  Sun. 

PERIHELION. 

From  this  first  law  of  Kepler,  it  results  that  the  planets  move  with  different  velocities, 
in  different  parts  of  their  orbits.  From  the  aphelion  to  the  perihelion  points,  the 
centripetal  force  combines  with  the  centrifugal  to  accelerate  the  planet's  motion ; 
while  from  perihelion  to  aphelion  points,  the  centripetal  acts  against  the  centrifugal 
force,  and  retdrcUi  it. 

The  tendency  to  depart  from  the  center?  What  does  the  joint  action  of  these  two  forces 
produce?  565.  What  relation  between  the  Sun's  attraction  and  the  centrifugal  force 
of  the  planets?  What  effect  has  the  distance  of  a  planet  from  the  Sun,  upon  his  attrac- 
tive force?  How  is  this  increased  tendency  counterbalanced?  566.  What  important 
laws — when  and  by  whom  discovered?  State  the  first?  What  are  the  apf^lioii  dnj 
ts?  Derivation?  What  results  from  this  first  law? 


LAWS    OF    PLANETARY    MO11ON. 


267 


RADIUS  VKCTOB. 


From  A  to  B  in  the  diagram,  the  centrifugal  force, 
represented  by  the  line  C,  acts  with  the  tendency  to 
revolve,  and  the  planet's  motion  is  accelerated;  but 
from  B  to  A  the  same  force,  shown  by  the  line  D,  acts 
against  the  tendency  to  advance,  and  the  planet  is 
retarded.  Hence  it  comes  to  aphelion  with  its  least 
Velocity,  and  to  perihelion  with  its  greatest. 

In  the  statement  of  velocities  on  page  45,  tbft  mean 
or  average  velocity  is  given. 

567.  The  second  law  is,  that  the  radius 
vector  of  a  planet  describes  equal  areas  in 
equal  times.     The  radius  is  an  imaginary 
Hue  joining  the  center  of  the  Sun  and 
the  center  of  the  planet,  in  any  part  of 
its  orbit.      Vector  is  from  veko,  to  carry  ; 
hence  the  radius  vector  is  a  radius  carried 

round.  By  the  statement  that  it  describes  equal  areas  in  equal 
times,  is  meant  that  it  sweeps  over  the  same  surface  in  an  hour, 
when  a  planet  is  near  the  Sun,  and  moves  swiftly,  as,  when 
furthest  from  the  Sun,  it  moves  mosfr  slowly. 

The  nearer  a  planet  is  to  the  Sun,  the  more  rapid  its 
motion.  It  follows,  therefore,  that  if  the  orbit  of  a 
planet  is  an  ellipse,  with  the  Sun  in  one  of  the  foci,  its 
rate  of  motion  will  be  unequal  in  different  parts  of  its 
orbit — swiftest  at  perihelion,  and  slowest  at  aphelion. 
From  perihelion  to  aphelion  the  centripetal  more  di- 
rectly counteracts  the  centrifugal  force,  and  the  planet 
is  retarded.  On  the  other  hand,  from  the  aphelion  to 
the  perihelion  point,  the  centripetal  and  centrifugal 
forces  are  united,  or  act  in  a  similar  direction.  They 
consequently  hasten  the  planet  onward,  and  its  rate  of 
motion  is  constantly  accelerated.  Now  suppose,  when  t 
the  planet  is  at  a  certain  point  near  its  perihelion,  we 
draw  a  line  from  its  center  to  the  center  of  the  Sun. 
This  line  is  the  radius  vector.  At  the  end  of  one  day, 
for  instance,  after  the  planet  has  advanced  considera- 
bly in  its  orbit,  we  draw  another  line  in  the  same  man- 
ner to  the  Sun's  center,  and  estimate  the  area  between 
the  two  lines.  At  another  time,  when  the  planet  is  near 
its  aphelion,  we  note  the  space  over  which  the  radius  vector  travels  in  one  day,  and  esti- 
mate its  area.  On  comparison,  it  will  be  found,  that  notwithstanding  the  unequal 
velocity  of  the  planet,  and  consequently  of  the  radius  vector,  at  the  two  ends  of  the 
«:llipse,  the  area  over  which  the  radius  vector  has  traveled  is  the  same  in  both  cases. 
The  same  principle  obtains  in  every  part  of  the  planetary  orbits,  whatever  may  be  their 
ellipticity  or  the  mean  distance  of  the  planet  from  the  Sun ;  hence  the  rule  that  the 
radius  vector  describes  equal  areas  in  equal  times.  In  the  preceding  cut,  the  twelve 
triangles,  numbered  1,  2,  8,  &c.,  over  each  of  which  the  radius  vector  sweeps  in  equal 
times,  are  equal. 

568.  The  third  law  of  Kepler  is,  that  the  squares  of  the  periodic 
times  of  any  two  planets  are  proportioned  to  the  cubes  of  their  mean 
distances  from  the  Sun. 

Take,  for  example,  the  Earth  and  Mars,  whose  periods  are  365-2564  and  686-9796  days, 
and  whose  distances  from  the  Sun  are  in  the  proportion  of  1  to  1-52369,  and  it  will  be 
found  that  (865.2564)2:  (686.9796)-! ::  (1)3  :  (1.52369)3. 

667.  State  the  second  law  of  Kepler?  Explain  it?  5C8.  The  third  'aw?  What 
illustration  ? 

B.G.        12 


}>68  ASTRONOMY. 

• 

According  to  these  laws,  which  are  known  to  prevail  throughout  the  solar  syotcai. 
many  of  the  facts  of  astronomy  are  deduced  from  other  facts  previously  ascertained. 
They  are,  therefore,  of  great  importance,  and  should  be  studied  till  they  are,  at  least, 
thoroughly  understood,  if  not  committed  to  memory. 

569.  From  the  foregoing  principles,  it  follows,  that  the  force 
of  gravity,  and  the  centrifugal  force,  are  mutual  opposing  powers 

each  continually  acting  against  the  other.     Thus,  the  weight 

of  bodies  on  the  Earth's  equator,  is  diminished  by  the  centrifugal 
force  of  her  diurnal  rotation,  in  the  proportion  of  one  pound  for 
every  290  pounds  :  that  is,  had  the  Earth  no  motion  on  her 
axis,  all  bodies  on  the  equator  would  weigh  one  two  hundred  and 
eighty-ninth  part  more  than  they  now  do. 

On  the  contrary,  if  her  diurnal  motion  were  accelerated,  the  centrifugal  force  would  be 
proportionally  increased,  and  the  weight  of  bodies  at  the  equator  would  be  in  the  same 
ratio  diminished.  Should  the  Earth  revolve  upon  its  axis  with  a  velocity  which  would 
make  the  day  but  84  minutes  long,  instead  of  24  hours,  the  centrifugal  force  would  coun- 
terbalance that  of  gravity,  and  all  bodies  at  the  equator  would  then  be  absolutely  desti- 
tute of  weight;  and  if  the  centrifugal  force  were  further  augmented  (the  Earth  revolving 
In  less  than  84  minutes),  gravitation  would  be  completely  overpowered,  and  all  fluids 
and  loose  substances  near  the  equator  would  fly  off  from  the  surface. 

570.  The  weight  of  bodies,  either  upon  the  Earth,  or  on  any 
other  planet  having  a  motion  around  its  axis,  depends  jointly 
upon  the  mass  of  the  planet,  and  its  diurnal  velocity.     A  body 
weighing  one  pound  upon  the  equator  of  the  -Earth,  would 
weigh,  if  removed  to  the  equator  of  the  Sun,  27.91bs.;  of  Mer^ 
cury,  1.03  Ibs.;  of  Venus,  0.98  Ibs.;  of  the  Moon,  l-6th  of  a-lb.  ; 
of  Mars,  |  Ib.  ;  of  Jupiter,  2.716  Ibs. ;  of  Saturn,  1.01  Ibs. 


CHAPTER  XI. 

PKOPER  MOTION  OF  THE  SUN  IN  SPACE. 

571.  THOFGH  we  are  accustomed  to  speak  of  the  Sun  as  tho 
fixed  center  of  the  Solar  System,  the  idea  of  his  fixedness  is  cor- 
rect only  so  far  as  his  relation  to  the  bodies  revolving  around 
him  are  concerned.  As  the  planets  accompanied  by  their  satel- 
lites revolve  around  the  Sun,  so  he  is  found  to  be  moving  with 
all  his  retinue  of  worlds,  in  a  vast  orbit,  around  some  distant  and 
unknown  center. 

669.  What  results  from  these  principles,  as  respects  the  weight  of  bodies  on  the  Ekrth'a 
surface?  How  increased  or  diminished?  What  illustrations  given?  570.  Upon 
7 hat,  then,  does  the  weight  of  bodies  upon  the  planets  depend?  What  illustrations ? 
CT1.  la  the  Sun  a  fixed  body?  What  motion  in  space?  Who  first  advanced  this  idea? 


PROPER    MOTION    OF    THE    SUN    IN    SPACE.  269 

This  opinion  was  first  advanced,  we  think,  by  Sir  William  Herschel;  but  the  honor  of 
actually  determining  this  interesting  fact,  belongs  to  Struve,  who  ascertained  not  only 
.he  direction  of  the  Sun  and  Solar  System,  but  also  their  velocity.  The  point  of  tend- 
ency is  towards  the  constellation  Hercules,  Right  Ascension  259*,  Declination  35*.  The 
velocity  of  the  Sun,  Ac.,  in  space,  is  estimated  at  about  20,000  miles  per  hour,  or  uearly 
S  miles  per  second ; 

572.  With  this  wonderful  fact  in  view,  we  may  no  longer  con- 
sider the  Sun  as  fixed  and  stationary,  but  rather  as  a  vast  and 
luminous  planet,  sustaining  the  same  relation  to  some  central 
orb,  that  the  primary  planets  sustain  to  him,  or  that  the  second- 
aries sustain  to  their  primaries.     !Nor  is  it  necessary  that  the 
stupendous  mechanism  of  nature  should  be  restricted  even  to 
these  sublime  proportions.     The  Sun's  central  body  may  also 
have  its  orbit,  and  its  center  of  attraction  and  motion,  and  so  on, 
till,  as  Dr.  Dick  observes,  we  come  to  the  great  center  of  all — to 
the  THRONE  OF  GOD. 

THE    CENTRAL     SUN. 

573.  In  1847,  an  article  appeared  in  several  European  jour- 
nals, announcing  the  probable  discovery  by  Professor  Madler, 
of  Dorpat,  of  the  Sun's  central  orb  ;  the  inclination  of  his  orbit 
to  the  plane,  of  the  ecliptic  ;  and  his  periodic  time  ! 

By  an  extensive  and  laborious  comparison  of  the  quantities 
and  directions  of  the  proper  motions  of  the  stars  in  various  parts 
of  the  heavens,  combined  with  indications  afforded  by  the  paral- 
laxes hitherto  determined,  and  with  the  theory  of  universal  gra- 
vitation, Professor  Madler  arrived  at  the  conclusion  that  the 
Pleiades  form  the  central  group  of  our  whole  astral  or  sidereal 
system,  including  the  Milky  Way  and  all  the  brighter  stars,  but 
exclusive  of  the  more  distant  nebula?,  and  of  the  stars  of  which 
those  nebula?  may  be  composed.  And  within  this  central  group 
itself  he  has  been  led  to  fix  on  the  star  Alcyone,  as  occupying 
exactly  or  nearly  the  position  of  the  center  of  gravity,  and  as 
entitled  to  be  called  the  central  Sun. 

Assuming  Bessel's  parallax  of  the  star  61  Cygni,  long  since  remarkable  for  its  larger 
proper  motion,  to  be  correctly  determined,  Madler  proceeds  to  form  a  first  approximate 
estimate  of  the  distance  of  this  central  body  from  the  planetary  or  solar  system ;  and 
arrives  at  the  provisional  conclusion,  that  Alcyone  is  about  34,000,000  times  as  far  removed 
from  us,  or  from  our  own  Sun,  as  the  latter  luminary  is  from  us.  It  would,  therefore 
according  to  this  estimation,  be  at  least  a  million  times  as  distant  as  the  new  planet,  of 
which  the  theoretical  or  deductive  discovery  has  been  so  great  and  beautiful  a  triumph 
of  modern  astronomy,  and  so  striking  a  confirmation  of  the  Jaw  of  Newton.  The  same 
approximate  determination  of  distance  conducts  to  the  result,  that  the  light  of  the  cen 
tral  sun  occupies  more  than  five  centuries  in  travelling  thence  to  us. 


Direction  and  velocity  of  the  Sun  and  Solar  System  ?  572.  How,  then,  should  w< 
regard  the  Sun?  What  further  speculation?  Dr.  Dick's  observation?  573.  What 
great  discovery  in  1847,  and  by  whom?  By  what  process?  What  conclusion  first 
reached  ?  What  star  afterward  designated  ?  Further  description  of  the  progress  of  the 
discovery  ?  What  conclusion  respecting  the  passage  of  light  from  the  sentral  Sun  to  ua  ? 


270 


ASTRONOMY 


,   .,  ARC    OF    THB    SUN'S    OBDIT 

574.  The  enormous  orbit 
which  our  own  Suu,  with  the 
Earth,  and  the  other  planets, 
is  thus  inferred  to  be  describ- 
ing about  that  distant  cen- 
ter— not,  indeed,  under  its 
influence  alone,  but  by  the 
combined  attractions  of  all 
the  stars  which  are  nearer  to 
it  than  we  are,  and  which  are 
estimated  to  amount  to  more 
than  117,000,000  of  masses, 
each  equal  to  the  total  mass 
of  our  own  Solar  System — 
is  supposed  to  require  upwards 
of  eighteen  millions  of  years  for 
its  complete  description,  at  the  rate  of  about  eight  geographical 
miles  in  every  second  of  time.  At  this  rate,  the  arc  of  its  orbit, 
over  which  the  Sun  has  traveled  since  the  creation  of  the  world, 
amounts  to  only  about  ^o^th  Par*  of  m's  orbit,  or  about  t 
minutes — an  arc  so  small,  compared  with  the  whole,  as  to  be 
hardly  distinguishable  from  a  straight  line. 

The  plane  of  this  vast  orbit  of  the  Sun  is  judged  to  have  an  inclination  of  about  84 
degrees  to  the  ecliptic,  or  to  the  plane  of  the  annual  orbit  of  the  Earth ;  and  the  longitude 
of  the  ascending  node  of  the  former  orbit  on  the  latter  is  concluded  to  be  nearly  232 
degrees. 


CHAPTER  XII. 

PRECESSION  OF  THE  EQUINOXES— OBLIQUITY   OF  THE 
ECLIPTIC. 

575.  OF  all  the  motions  which  are  going  forward  in  the  Solar 
System,  there  is  none,  which  it  is  important  to  notice,  more 
difficult  to  comprehend,  or  to  explain,  than  what  is  called  the 

PRECESSION    OF   THE    EQUINOXES. 

The  equinoxes,   as  we  have  learned,  are  the  two  opposite 

574.  Supposed  period  of  the  Sun's  revolution  ?  What  portion  of  his  orbit  gone  over 
Jince  the  creation  of  our  race?  Situation  of  his  orbit  with  respect  to  the  ecliptic?  Lon- 
gitude of  ascending  node?  575.  Subject  of  this  chapter?  What  are  the  equinoxes ? 


PRECESSION    OF    THE    EQUINOXES. 


271 


points  in  the  Earth's  orbit,  where  it  crosses  the  celestial  equator. 
The  first  is  in  Aries  ;  the  other,  in  Libra.  By  the  precession  of  the 
equinoxes  is  meant,  that  the  intersection  of  the  equator  with  the 
ecliptic  is  not  always  in  the  same  point  :  —  in  other  words,  that 
the  Sun,  in  its  apparent  annual  course,  does  not  cross  the  equi- 
noctial, Spring  and  Autumn,  exactly  in  the  same  points,  but 
every  year  a  little  behind  those  of  the  preceding  year. 

576.  This  annual  falling  back  of  the  equinoctial  points,  is 
called  by  astronomers,  with  reference  to  the  motion  of  the 
heavens,  the  Precession  of  the  Equinoxes;  but  it  would  better 
accord  with  fact  as  well  as  the  apprehension  of  the  learner,  to 
call  it,  as  it  is,  the  Recession  of  the  Equinoxes  ;  for  the  equinoc- 
tial points  do  actually  recede  upon  the  ecliptic,  at  the  ra>e  of 
about  50£"  of  a  degree  every  year.  It  is  the  name  only,  and 
not  the  position,  of  the  equinoxes  which  remains  permanent. 
Wherever  the  Sun  crosses  the  equinoctial  in  the  spring,  there  is 
the  vernal  equinox  ;  and  wherever  he  crosses  it  in  the  autumn, 
there  is  the  autumnal  equinox  \  and  these  points  are  constantly 
moving  to  the  west. 

PRECESSION  OF  THE  EQUINOXES. 


To  render  this  subject  familiar, 
we  will  suppose  two  carriage  roads, 
extending  quite  around  the  Earth; 
one,  representing  the  equator,  run- 
ning due  east  and  west;  and  the 
other  representing  the  ecliptic,  run- 
ning nearly  in  the  same  direction  as 
the  former,  yet  so  as  to  cross  it  with 
a  small  angle  (say  of  2333°),  both  at 
the  point  where  we  now  stand,  for 
instance,  and  in  the  nadir,  exactly 
opposite  ;  let  there  also  be  another 
road,  to  represent  the  prime  meri- 
dian, running  north  and  south,  and 
erasing  the  first  at  right  angles,  in 
the  common  point  of  intersection,  as 
in  the  annexed  figure. 

Let  a  carriage  now  start  from  this 
point  of  intersection,  not  in  the  road 
leading  directly  east,  but  along  that 
of  the  ecliptic,  which  leaves  the 
former  a  little  to  the  north,  and  let 
a  person  >>e  placed  to  watch  when 
the  carriage  comes  around  again, 
after  having  made  the  circuit  of  the 
Earth,  and  see  whether  the  carriage 
will  cross  the  equinoctial  road  again 
precisely  in  the  same  track  as  when  it  left  the  goal.  Though  the  person  stood  exactly 
in  the  former  track,  he  need  not  fear  being  run  over,  for  the  carriage  will  cross  the 
road  100  rods  west  of  him,  that  is  100  rods  west  of  the  meridian  on  which  he  stood.  It  is 
to  be  observed,  that  100  rods  on  the  equator  is  equal  to  50  i£  seconds  of  a  degree. 

If  the  carriage  still  continue  to  go  around  the  Earth,  it  will,  on  completing  its  second 


What  meant  by  their  precession  ?  576.  With  reference  to  what  is  it  a  preccf&ionf  Id 
it  really  a  precession  of  the  equinoxes  ?  Where  are  the  equinoxes  spring  and  fall  ?  Can 
you  illustrate  by  the  two  carriage  roads,  &c.  ?  By  the  other  diagram?  Does  the  £>un 


272 


ASTRONOMY. 


RECESSION  OF  THE  EQUINOXES. 


circuit,  cross  the  equinoctial  path  200  rods  west  of  the  meridian  whence  it  first  set  out 
on  the  third  circuit,  300  rods  west ;  on  the  fourth  circuit,  400  rods,  and  so  on,  continually. 
After  71%  circuits,  the  point  of  intersection  would  be  one  degree  west  of  its  place  at  the 
commencement  of  the  route.  At  this  rate  it  would  be  easy  to  determine  how  many  com- 
plete circuits  the  carriage  must  perform  before  this  continual  falling  back  of  the  inter- 
secting point  would  have  retreated  over  every  degree  of  the  orbit,  until  it  reached  again 
the  point  from  whence  it  first  departed.  The  application  of  this  illustration  will  be  mani- 
fest when  we  consider,  further, 
that  this  interesting  phenomenon 
may  be  explained  in  another 
way  by  the  a<ijoining  diagram. 
Let  the  point  A  represent  the 
vernal  equinox,  reached,  for  in- 
stance, at  12  o'clock  on  the  20th 
of  March.  The  next  year  the 
Sun  will  b'e  in  the  equinoctial  22 
minutes  33  seconds  earlier,  at 
which  time  the  Earth  will  be 
50%"  on  the  ecliptic,  back  of  the 
point  at  which  the  Sun  was  in 
the  equinoctial  the  year  before. 
The  next  year  the  same  will  oc- 
cur again ;  and  thus  the  equi- 
noctial point  will  recede  west- 
ward little  by  little,  as  shown  by 
the-  small  lines  from  A  to  B,  and 
from  C  to  I).  It  is  in  reference 
to  the  stars  going  forward,  or 
seeming  to  precede  the  equi- 
noxes, that  the  phenomenon  is 
called  the  Precession  of  the  Equi- 
noxes. But  in  reference  to  the 
motion  of  the  equinoxes  them- 
telves,  it  is  rather  a  recession. 

577.  The  Sun  revolves  from  one  equinox  to  the  same  equinox 
again,  in  365d.  5h.  48'  47"  81.  This  constitutes  the  natural,  or 
tropical  year,  because,  in  this  period,  one  revolution  of  the  sea- 
sons is  exactly  completed.  But  it  is,  meanwhile,  to  be  borne  in 
mind,  that  the  equinox  itself,  during  this  period,  has  not  kept 
its  position  among  the  stars,  but  has  deserted  its  place,  and 
fallen  lack  a  little  way  to  meet  the  Sun  ;  whereby  the  Sun  has 
arrived  at  the  equinox  before  he  has  arrived  at  the  same  position 
among  the  stars  from  which  he  departed  the  year  before  ;  and, 
consequently,  must  perform  as  much  more  than  barely  a  tropical 
revolution,  to  reach  that  point  again. 

To  pass  over  this  interval,  which  completes  the  Sun's  sidereal 
revolution,  takes  (20'  22".94)  about  22  minutes  and  23  seconds 
longer.  By  adding  22  minutes  and  23  seconds  to  the  time  of  a 
tropical  revolution,  we  obtain  365d.  6h.  9m.  lOfs.  for  the  length 
of  a  sidereal  revolution ;  or  the  time  in  which  the  Sun  revolves 
from  one  fixed  star  to  the  same  star  again. 

Though  we  speak  of  the  revolution  of  the  Fun,  we  mean  simply  his  apparent  revolution 
eastward  around  the  heavens,  caused  wholly  by  the  actual  revolution  of  the  Earth  in  her 

actually  revolve?  Why,  then,  speak  of  his  revolution?  577.  What  is  the  length  of  a 
tropical  year  ?  How  different  from  a  sidereal  year  ?  Difference  of  time  T  Length  of  a 
aidereal  year  ? 


PRECESSION  OF  THE  EQUINOXES. 


273 


orbit,  aa  a  distant  object  would  appear  to  sweep  around  the  horizon  if  we  were  walking 
or  sailing  around  it.  This  may  be  illustrated  by  the  cut,  page  288-  where  the  passage 
of  the  Earth  from  A  to  B  would  cause  the  Sun  to  appear  to  move  from  C  to  D  j  and  S3  on 
around  the  whole  circle  of  the  Zodiac. 

578.  As  the  Sun  describes  the  whole  ecliptic,  or  360°,  in  a 
tropical  year,  he  moves  over  59'  8£"  of  a  degree  every  day,  at  a 
mean  rate,  which  is  equal  to  50^"  of  a  degree  in  20  minutes  and 
23  seconds  of  time  ;  consequently  he  will  arrive  at  the  same 
equinox  or  solstice  when  he  is  50£"  of  a  degree  short  of  the.  same 
star  or  fixed  point  in  the  heavens,  from  which  he  set  out  the 
year  before.  So  that,  with  respect  to  the  fixed  stars,  the  Suii 
and  equinoctial  points  fall  back,  as  it  were,  1°  in  7  If  years. 
This  will  make  the  stars  appear  to  have  gone  forward  1°,  with 
respect  to  the  signs  in  the  ecliptic,  in  that  time  ;  for  it  must  be 
observed,  that  the  same  signs  always  keep  in  the  same  points  of  the 
ecliptic,  without  regard  to  the  place  of  the  constellations.  Hence  it 
becomes  necessary  to  have  new  plates  engraved  for  celestial 
globes  and  maps,  at  least  once  in  50  years,  in  order  to  exhibit 
truly  the  altered  position  of  the  stars.  At  the  present  rate  of 
motion,  the  recession  of  the  equinoxes,  as  it  should  be  called,  or 
the  precession  of  the  stars,  amounts  to  30°,  or  one  whole  sign,  in 
2140  years. 


PRECESSION    OP    THE    STABS. 


To  explain  this  by  a  figure :  Suppose  the  Sun  to  have  been  in  conjunction  with  a  fixea 
star  at  S,  in  the  first  degree  of  Taurus  (the  second  sign  of  the  ecliptic),  840  years  before 
the  birth  of  our  Saviour,  or  about  the  seventeenth  year  of  Alexander  the  Great;  then 
having  made  2140  revolutions  through  the  ecliptic,  he  would  be  found  again  at  the  end  of 
so  many  sidereal  years  at  S ;  but  at  the  end  of  so  many  Julian  years,  he  would  be  found 
at  J,  and  at  the  end  of  so  many  tropical  years,  which  would  bring  it  down  to  the  begin- 
ning of  the  present  century,  he  would  be  found  at  T,  in  the  first  degree  of  Aries,  which 


578.  Daily  progress  of  the  Sun  ?  What  is  the  amount  of  the  annual  recession  of  the 
equinoxes  ?  What  effect  will  this  have  upon  the  apparent  positions  of  the  stars  ?  Hence 
what  becomes  necessary?  How  long  does  it  require  for  the  equinoxes  to  recede  a  wiolo 
sign  ?  Do  you  understand  the  diagram,  and  the  reference  to  the  sidereal,  Julian,  aud 
Tropical  years?  Explain  the  difference  in  the«=e  three  kinds  of  yeara. 


274  ASTRONOMY. 

has  receded  from  S  to  T  in  that  time  by  the  precession  of  the  equinoctial  points  Aries  anU 
Libra.  The  arc  S  T  would  be  equal  to  the  amount  of  the  precession  (for  precession  we 
must  still  call  it)  of  the  equinox  in  2140  years,  at  the  rate  of  50".23572  of  a  degree,  or  20 
minutes  and  23  seconds  of  time  annually,  as  above  stated. 

519.  From  the  constant  retrogradation  of  the  equinoctial 
points,  and  with  them  of  all  the  signs  of  the  ecliptic,  it  follows 
that  the  longitude  of  the  stars  must  continually  increase.  The  same 
cause  affects  also  their  right  ascension  and  declination.  Hence, 
those  stars  which,  in  the  infancy  of  astronomy,  were  in  the  sign 
Aries,  we  now  find  in  Taurus  ;  and  those  which  were  in  Taurus, 
we  now  find  in  Gemini,  and  so  on.  Hence  likewise  it  is,  that 
the  star  which  rose  or  set  at  any  particular  time  of  the  year,  ID. 
the  time  of  Hesiod,  Eudoxus,  Yirgil,  Pliny,  and  others,  by  110 
means  answers  at  this  time  to  their  descriptions. 

Hesiod,  in  his  Opera  et  Dies,  lib.  ii.  verse  185,  says : 

"  When  from  the  solstice  sixty  wintry  days 
Their  turns  have  finished,  mark,  with  glitt'ring  rays, 
From  Ocean's  sacred  flood,  Arcturus  rise, 
Then  first  to  gild  the  dusky  evening  skies." 

But  Arcturus  now  rises  acronically  in  latitude  37°  45'  N.  the  latitude  of  Hesiod,  ana 
nearly  that  of  Richmond,  in  Virginia,  about  100  days  after  the  winter  solstice.  Suppos- 
ing Hesiod  to  be  correct,  there  is  a  difference  of  40  days  arising  from  the  precession  of 
the  equinoxes  since  the  days  of  Hesiod.  Now,  as  there  is  no  record  extan,t  of  the  exact 
period  of  the  world  when  this  poet  flourished,  let  us  see  to  what  result  astronomy  will 
lead  us. 

As  the  Sun  moves  through  about  39°  of  the  ecliptic  in  40  days,  the  winter  solstice,  in 
the  time  of  Hesiod,  was  in  the  9th  degree  of  Aquarius.  Now,  estimating  the  precession 
of  the  equinoxes  at  50%"  in  a  year,  we  shall  have  503^*  :  1  year : :  39  :  2814 years  since  the 
time  of  Hesiod  :  if  we  subtract  from  this  our  present  era,  1855,  it  will  give  958  years  before 
Christ.  Lempriere,  in  his  Classical  Dictionary,  says  Hesiod  lived  907  years  before  Christ. 
See  a  similar  calculation  for  the  time  of  Thales,  page  39. 

580.  The   retrograde   movement  of   the   equinoxes,  and  the 
annual  extent  of  it,  were  determined  by  comparing  the  longitude 
of  the  same  stars,  at  different  intervals  of  time.     The  most  care- 
ful and  unwearied  attention  was  requisite  in  order  to  determine 
the  cause  and  extent  of  this  motion — a  motion  so  very  slow  as 
scarcely  to  be  perceived  in  an  age,  and  occupying  not  less  than 
25,000  years  in  a  single  revolution.     It  has  not  yet  completed 
one  quarter  of  its  first  circuit  in  the  heavens  since  the  creation 
of  Mars. 

581.  This  observation  has  not  only  determined  the  absolute 
motion  of  the  equinoctial  points,  but  measured  its  limit  ;  it  has 
also  shown  that  this  motion,  like  the  causes  which  produce  it,  is 
not  uniform  in  itself  ;  but  that  it  is  constantly  accelerated  by  a 

579.  What  effect  has  the  recession  of  the  equinoxes  upon  the  longitude  of  the  stars,  and 
their  right  ascension  and  declination  ?  Hence  what  results  ?  What  interesting  calcu- 
lation in  reference  to  Hesiod  ?  580.  How  were  this  recession  and  its  extent  determined  ? 
What  necessary?  Time  of  complete  revolution?  Amount  since  creation?  681.  Ie 
this  retrogression  uniform?  Amount  of  acceleration  ?  What  illustration  given  ? 


PRECESSION    OF    THE    EQUINOXES.  275 

islow  arithmetical  increase  of  I"  of  a  degree  in  4100  years.  A 
quantity  which,  though  totally  inappreciable  for  short  periods  of 
time,  becomes  sensible  after  a  lapse  of  ages. 

For  example  :  The  retrogradation  of  the  equinoctial  points  is  now  greater  by  nearlj  Jg' 
xhan  it  was  in  the  time  of  Hipparchus,  the  first  who  observed  this  motion ;  consequently, 
the  mean  tropical  year  is  shorter  now  by  about  12  seconds  than  it  was  then.  For,  since 
the  retrogradation  of  the  equinoxes  is  now  every  year  greater  than  it  was  then,  the  Sun 
has,  each  year,  a  space  of  nearly  Jg"  less  to  pass  through  in  the  ecliptic,  in  order  to  reach 
the  plane  of  the  equator.  Now  the  Sun  is  12  seconds  of  time  in  passing  over  %'  of  space. 

582.  At  present,  the  equinoctial  points  move  backwards,  or 
from  east  to  west  along  the  path  of  toe  ecliptic  at  the  rate  of  1° 
in  7  If  years,  or  one  whole  sign  in  2140  years.     Continuing  at 
this  rate,  they  will  fall  back  through  the  whole  of  the  12  signs 
of  the  ecliptic  in  25,680  years,  and  thus  return  to  the  same  posi- 
tion among  the  stars,  as  in  the  beginning. 

But  in  determining  the  period  of  a  complete  revolution  of  the 
equinoctial  points,  it  must  be  borne  in  mind  that  the  motion  itself 
is  continually  increasing;  so  that  the  last  quarter  of  the  revolu- 
tion is  accomplished  several  hundred  years  sooner  than  the  first 
quarter.  Making  due  allowance  for  this  accelerated  progress, 
the  revolution  of  the  equinoxes  is  completed  in  25,000  years  ; 
or,  more  exactly,  in  24,992  years. 

Were  the  motion  of  the  equinoctial  points  uniform ;  that  is,  did  they  pass  through 
equal  portions  of  the  ecliptic  in  equal  times,  they  would  accomplish  their  first  quarter,  or 
pass  through  the  first  three  signs  of  the  ecliptic,  in  6250  years.  But  they  are  6575  years 
in  passing  through  the  first  quarter ;  about  218  years  less  in  passing  through  the  second 
quarter;  218  less  in  passing  through  the  third, and  so  on. 

583.  The  immediate  consequence  of  the  precession  of  the  equi- 
noxes, as  we  have  already  observed,  is  a  continually  progressive 
increase  of  longitude  in  all  the  heavenly  bodies.     For  the  vernal 
equinox  being  the  initial  point  of  longitude,  as  well  as  o*  right 
ascension,  a  retreat  of  this  point  on  the  ecliptic  tells  upon  the 
longitude  of  all  alike,  whether  at  rest  or  in  motion,  and  pro- 
duces, so  far  as  its  amount  extends,  the  appearance  of  a  motion 
in  longitude  common  to  them  all,  as  if  the  whole  heavens  had  a 
slow  rotation  around  the  poles  of  the  ecliptic  in  the  long  period 
above  mentioned,  similar  to  what  they  have  in  every  twenty-four 
hours  around  the  poles  of  the  equinoctial.     As  the  Sun  loses  one 
day  in  the  year  on  the  stars,  by  his  direct  motion  in  longitude  ; 
so  the  equinox  gains  one  day  on  them  in  25,000  years,  by  its 
retrograde  motion. 

582.  Present  rate  of  motion  ?  Exact  period  at  W»ls  rate  ?  Period  making  allowance 
for  acceleration?  Time  of  passing  over  the  first  quarter  of  the  ecliptic?  The  second? 
Third?  533.  What  immediate  consequences  of  the  precession  of  the  equinoxes? 
Why  does  it  affe-  the  longitude  of  the  stars  ?  What  resemblance  between  the  motion  of 
the  celestial  spher  and  that  of  the  Earth  ?  Between  the  Sun  and  equinoxes? 

12* 


276 


ASTRONOMY. 


584.  The  cause  of  this  motion  was  unknown,  until  Aewton 
proved  that  it  was  a  necessary  consequence  of  the  rotation  of 
the  Earth,  combined  with  its  elliptical  figure,  and  the  unequal 
attraction  of  the  Sun  and  Moon  on  its  polar  and  equatorial 
regions.     There  being  more  matter  about  the  Earth's  equator 
than  at  the  poles,  the  former  is  more  strongly  attracted  than 
the  latter,  which  causes  a  slight  gyratory  or  wabbling  motion  of 
the  poles  of  the  Earth  around  those  of  the  ecliptic,  like  the  pin 
of  a  top  about  its  center  of  motion,   when  it  spins  a  little 
obliquely  to  the  base. 

585.  The  precession  of  the  equinoxes,  thus  explained,  consists 
in  a  real  motion  of  the  pole  of  the  heavens  among  the  stars,  in  a 
small  circle  around  the  pole  of  the  ecliptic  as  a  center,  keeping 
constantly  at  its  present  distance  of  nearly  23£°  from  it,  in  a 
direction  from  east  to  west,  and  with  a  progress  so  very  slow, 
as  to  require  25,000  years  to  complete  the  circle.     During  this 
revolution,  it  is  evident  that  the  pole  will  point  successively  to 
every  part  of  the  small  circle  in  the  heavens  which   it  thus 
describes.     Now  this  cannot  happen  without  producing  corre- 
sponding changes  in  the  apparent  diurnal  motion  of  the  sphere, 
and  in  the  aspect  which  the  heavens  must  present  at  remote 
periods  of  time. 


NUTATION  OF  THB  EARTH'S  AXIS. 
B 


Let  the  line  A  A  in  the  figure  re- 
present the  plane  of  the  ecliptic; 
B  B,  tne  poles  of  the  ecliptic ;  C  C, 
the  poles  of  the  Earth  ;  and  D  D,  the 
equin  -dial.  &  E  is  the  obliquity  of 
the  ecliptic.  The  star  C,  at  the  top, 
represents  the  pole  star,  and  the 
curve  Mne  passing  to  the  right  from 
it,  may  represent  the  circular  orbit 
of  the  north  pole  of  the  hearens 
around  the  north  pole  of  the  ecliptic. 

586.  The  effect  of  such 
a  motion  on  the  aspect  of 
the  heavens,  is  seen  in  the 
apparent  approach  of  some 
stars  and  constellations  to 
the  celestial  pole,  and  the 
recession  of  others.  The 
bright  star  of  the  Lesser 
Bear,  which  we  call  the  pole  star,  has  not  always  been,  nor  will 
always  continue  to  be,  our  polar  star.  At  the  time  of  the  con- 

584.  What  said  of  the  cause  of  this  recession?  585.  0  what,  then,  does  it  consist? 
What  said  of  the  pole  of  the  ecliptic,  and  the  aspects  of  t».  neavens  during  this  revolu- 
tion? 685.  How  is  the  effect  of  this  motion  manifos  <»d?  How  with  the  Pole  star  if 


PRECESSION    OF    THE    EQUINOXES.  277 

struction  of  the  earliest  catalogue,  this  star  was  12°  from  the 
pole  ;  it  is  now  only  1°  34'  from  it,  and  it  will  approach  to 
within  half  a  degree  of  it  ;  after  which  it  will  again  recede,  and 
slowly  give  place  to  others,  which  will  succeed  it  in  its  proximity 
to  the  pole. 

The  pole,  as  above  considered,  is  to  be  understood,  merely,  as  the  vanishing  point  of 
the  Earth's  axis;  or  that  point  in  the  concave  sphere  which  is  always  opposite  the 
terrestial  pole,  and  which  consequently  must  move  as  that  moves. 

587.  The  precession  of  the  stars  in  respect  to  the  equinoxes, 
is  less  apparent  the  greater  their  distance  from  the  ecliptic  ;  for 
whereas  a  star  in  the  zodiac  will  appear  to  sweep  the  whole 
circumference  of  the  heavens  in  an  equinoctial  year,  a  star  situ- 
ated within  the  polar  circle  will  describe  only  a  very  small  circle 
in  that  period,  and  by  so  much  the  less,  as  it  approaches  the 
pole.     The  north  pole  of  the  Earth  being  elevated  23°  27|' 
towards  the  tropic  of  Cancer,  the  circumpolar  stars  will  be  suc- 
cessively at  the  least  distance  from  it,  when  their  longitude  i& 
3  signs  or  90°. 

588.  The  position  of  the  north  polar  star  in  1855,  was  in  the 
17°  of  Taurus;  when  it  arrives  at  the  first  degree  of  Cancer, 
which  it  will  do  in  about  250  years,  it  will  be  at  its  nearest 
possible  approach  to  the  pole — namely,  29'  55".     About  2900 
years  before  the  commencement  of  the  Christian  era,  Alpha  Dra- 
conis,  the  third  star  of  the  Dragon's  tail,  was  in  the  first  degree 
of  Cancer,  and  only  10'  from  the  pole  ;  consequently  it  was  then 
the  pole  star.     After  the  lapse  of  11,600  years  the  star  Lyra, 
the  brightest  in  the  northern  hemisphere,  will  occupy  the  position 
of  a  pole  star,   being   then  about  5  degrees  from  the  pole  ; 
whereas  now  its  north  polar  distance  is  upward  of  51°. 

The  mean  average  precession  from  the  creation  (4004  B.  C.)  to  the  year  1800,  is 
49'.51455;  consequently  the  equinoctial  points  have  receded  since  the  creation,  2s.  14*  8' 
27".  The  longitude  of  the  star  Seta  Arietiz,  was  in  1820,  81°  27'  28" :  Meton,  a  famous 
mathematician  of  Athens,  who  flourished  480  years  before  Christ,  says,  this  star,  in  his 
time,  was  in  the  vernal  equinox.  If  he  is  correct,  then  31°  27'  2S\  divided  by  2250  years, 
the  elapsed  time,  will  give  50 %"  for  the  precession.  Something,  however,  must  be 
allowed  for  the  imperfection  of  the  instruments  used  at  that  day,  and  even  until  the  six- 
teenth century. 

589.  Since  all  the  stars  complete  half  a  revolution  about  the 
axis  of  the  ecliptic  in  about  12,500  years,  if  the  North  Star  be 
at  its  nearest  approach  to  the  pole  250  years  hence,  it  will, 

What,  then,  is  the  real  pole  of  the  heavens  ?  587.  Where  is  the  precession  of  the  stara 
most  apparent?  Where  least?  When  are  the  circumpolar  stars  nearest  the  tropic  of 
Cancer,  and  why?  588.  Where  was  the  pole  star  in  1855?  When  will  it  be  neareat 
the  true  pole?  How  near  then?  What  said  of  Alpha  DraconU*  Of  Lyra  t  Mean 
average  recession  for  5800  years?  Amount?  Longitude  of  Bfta  A rieUs  in  1820?  Be- 
fore Christ  430  years,  where  ?  Average  of  precession  for  these  2250  years  ?  589.  What 
further  result  of  the  revolution  of  the  pole  of  the  heavens  ?  What  effect  ?  "ft  here,  then, 


279 


ASTRONOMY. 


12,500  years  afterwards,  be  at  its  greatest  possible  distance 
from  it,  or  about  47°  above  it : — That  is,  the  star  itself  will 
remain  immovable  in  its  present  position,  but  the  pole  of  the 
Earth  will  then  point  as  much  below  the  pole  of  -the  ecliptic,  as 
now  it  points  above.  This  will  have  the  effect,  apparently,  of 
elevating  the  present  polar  star  to  twice  its  present  altitude,  or 
47°.  Wherefore,  at  the  expiration  of  half  the  equinoctial  year, 
that  point  of  the  heavens  which  is  now  1°  18'  north  of  the  zenith 
of  Hartford,  will  be  the  place  of  the  north  pole,  and  all  those 
places  which  are  situated  1°  18'  north  of  HartfoH,  will  then 
have  the  present  pole  of  the  heavens  in  their  zenith. 

OBLIQUITY    OF   THE    ECLIPTIC. 

590.  The  inclination  of  the  Earth's  axis  to  the  plane  of  the 
ecliptic  causes  the  equinoctial  to  depart  23°  28'  from  the  eclip- 
tic. This  angle  made  by  the  equinoctial  and  the  ecliptic  is 
called  the  Obliquity  of  the  Ecliptic. 


OBLIQUITY  OP  THE  ECLIPTIC. 

A 


Let  the  line  A  A  represent 
the  axis  of  the  Earth,  and  fi  B 
the  poles  or  axis  of  the  eclip- 
tic. Now  if  the  line  A  A  in- 
clines  toward  the  plane  of  the 
ecliptic,  or,  in  other  words, 
departs  from  the  line  B«,  to 
the  amount  of  23°  28',  it  is 
obvious  that  the  plane  of  the 
equator,  or  equinoctial,  will  PLANE  Of 
depart  from  the  ecliptic  to  the  " 
same  amount.  This  depar- 
ture, shown  by  the  angles 
C  C,  constitute  the  obliquity 
of  the  ecliptic. 

591.  Hitherto,  we 
have  considered  these 
great  primary  circles 
in  the  heavens,  as  never  varying  their  position  in  space,  nor  with 
respect  to  each  other.  But  it  is  a  remarkable  and  well-ascer- 
tained fact,  that  both  are  in  a  state  of  constant  change.  We 
have  seen  that  the  plane  of  the  Earth's  equator  is  constantly 
drawn  out  of  place  by  the  unequal  attraction  of  the  Sun  and 
Moon  acting  in  different  directions  upon  the  unequal  masses  of 
matter  at  the  equator  and  the  poles  ;  whereby  the  intersection 
of  the  equator  with  the  ecliptic  is  constantly  retrograding—  thus 
producing  the  precession  of  the  equinoxes. 


590.  What  is  th-OWquityof 
the  same?    \Vhat  variation  of  the  equinoctial? 


PRECESSION  OF  'THE  EQUINOXES.  279 

592.  The  displacement  of  the  ecliptic,  on  the  contrary,  is  pro- 
duced chiefly  by  the  action  of  the  planets,  particularly  of  Jupi- 
ter and  Yenus,  on  the  Earth  ;  by  virtue  of  which  the  plane  of 
the  Earth's  orbit  is  drawn  nearer  to  those  of  these  two  planets, 
and  consequently,  nearer  to  the  plane  of  the  equinoctial.     The 
tendency  of  this  attraction  of  the  planets,  therefore,  is  to  dimi* 
nish  the  angle,  which  the  plane  of  the  equator  makes  with  that 
of  the  ecliptic,  bringing  the  two  planes  nearer  together  ;  and  if 
the  Earth  had  no  motion  of  rotation,  it  would,  in  time,  cause 
the  two  planes  to  coincide.     But  in  consequence  of  the  rotary 
motion  of  the  Earth,  the  inclination  of  these  planes  to  each  other 
remains  very  nearly  the  same  ;  its  annual  diminution  being  scarcely 
more  than  three-fourths  of  one  second  of  a  degree. 

The  obliquity  of  the  ecliptic,  at  the  commencement  of  the  present  century  was,  accord- 
ing to  Batty,  23°  27'  56  3£",  subject  to  a  yearly  diminution  of  0".4755.  According  to  Bes- 
6el,  it  was  23°  27'  54" .32,  with  an  annual  diminution  of  0".46.  At  this  date  (1855),  it  is  only 
about  23*  27'  29".  Consequently,  the  angle  is  diminished  about  27"  in  55  years.  This 
diminution,  however,  is  subject  to  a  slight  semi-annual  variation,  from  the  same  causes 
which  produce  the  displacement  of  the  plane  of  the  ecliptic,  in  precession. 

593.  The  attraction  of  the  Sun  and  Moon,  also,  unites  with 
that  of  the  planets,  at  certain  seasons,  to  augment  the  diminu- 
tion of  the  obliquity,  and  at  other  times,  to  lessen  it.     On  this 
account  the  obliquity  itself  is  subject  to  a  periodical  variation  ; 
for  the  attractive  power  of  the  Moon,  which  tends  to  produce  a 
change  in  the  obliquity  of  the  ecliptic,  is  variable,  while  the  diur- 
nal motion  of  the  Earth,  which  tends  to  prevent  the  change  from 
taking  place,  is  constant.     Hence  the  Earth,  which  is  so  nicely 
poised  on  her  center,  bows  a  little  to  the  influence  of  the  Moon, 
and   rises   again,   alternately,   like  the   gentle  oscillations  of  a 
balance.     This  curious  phenomenon  is  called  Nutation  (589). 

In  consequence  of  the  yearly  diminution  of  the  obliquity  of  the  ecliptic,  the  tropics  are 
slowly  and  steadily  approaching  the  equinoctial,  at  the  rate  of  little  more  than  three- 
fourths  of  a  second  every  year;  so  that  the  Sun  does  not  now  come  so  far  north  of  tl:e 
equator  in  summer,  nor  decline  so  far  south  in  winter,  by  nearly  a  degree,  as  it  must 
have  done  at  the  Creation. 

594.  The  most  obvious  effect  of  this  diminution  of  the  obli- 
quity of  the  ecliptic,  is  to  equalize  the  length  of  our  days  and 
nights  ;  but  it  has  an  effect  also  to  change  the  position  of  the 
stars  near  the  tropics.     Those   which  were  formerly  situated 
north  of  the  ecliptic,  near  the  summer  solstice,  are  now  found  to 
be  still  farther  north,  and  farther  from  the  plane  of  the  ecliptic. 
On  the  contrary,  those  which,  according  to  the  testimony  of  the 

592.  What  displacement  of  the  ecliptic,  and  by  what  caused  ?  Effect  of  these  causes  ? 
Amount  of  change  annually?  Obliquity  of  the  ecliptic  in  1800?  In  1855?  593.  Diminution 
In  55  years?  What  is  Nutation?  Its  cause?  What  effect  from  this  annual  diminu- 
tion of  obliquity?  594.  What  other  effect?  Will  this  diminution  continue?  What 


280 


ASTRONOMY. 


ancient  astronomers,  were  situated  south  of  the  ecliptic,  near  the 
summer  solstice,  have  approached  this  plane,  insomuch  that  some 
are  now  either  situated  within  it,  or  just  on  the  north  side  of  it. 
Similar  changes  have  taken  place  with  respect  to  those  stars 
situated  near  the  winter  solstice.  All  the  stars,  indeed,  partici- 
pated more  or  less  in  this  motion,  but  less,  in  proportion  to  their 
proximity  to  the  equinoctial. 

It  is  important,  however,  to  observe,  that  this  diminution  will  not  always  continue.  A 
time  will  arrive  when  this  motion,  growing  less  and  less,  will  at  length  entirely  cease, 
and  the  obliquity  will,  apparently,  remain  constant  for  a  time  ;  after  which  it  will  gra- 
dually increase  again,  and  continue  to  diverge  by  the  same  yearly  increment  as  it  before 
had  diminished.  This  alternate  decrease  and  increase  will  constitute  an  endless  oscilla- 
tion, comprehended  between  certain  fixed  limits.  Theory  has  not  yet  enabled  us  to 
determine  precisely  what  these  limits  are,  but  it  may  be  demonstrated  from  the  constitu- 
tion of  our  globe,  that  such  limits  exist,  and  that  they  are  very  restricted,  probably  not 
exceeding  2°  42'.  If  we  consider  the  effect  of  this  ever-varying  attribute  in  the  system 
of  the  universe,  it  may  be  affirmed  that  the  plane  of  the  ecliptic  never  has  coincided 
with  the  plant?  of  the  equator,  and  never  will  coincide  with  it.  Such  a  coincidence, 
could  it  happen,  would  produce  upon  the  Earth  perpetual  spring. 

595.  The  method  used  by  astronomers  to  determine  the 
obliquity  of  the  ecliptic  is,  to  take  half  the  difference  of  the 
greatest  and  least  meridian  altitudes  of  the  Sun. 

The  following  table  exhibits  the  mean  obliquity  of  the  ecliptic  for  every  ten  years 
during  the  present  century. 


1800 
1810 
1820 
1830 
1840 
1850 

23" 
23 
23 
23 
23 
23 

27' 
27 
27 
27 
27 
27 

54".  78 
50  .21 
45  .64 
41  .07 
36  .50 
31  .93 

1860 
1870 
1880 
1890 
1900 
1910 

23" 
28 
23 
23 
23 
23 

27' 
27 
27 
27 
27 
27 

27'  .36 
22  .79 
18  .22 
13  .65 
09  .08 
04  .52 

CHAPTER  XIII. 

PHILOSOPHY  OF  THE  TIDES. 

596.  TIDES  are  the  alternate  rising  and  falling  of  the  waters 
of  the  ocean,  at  regular  intervals.  Flood  tide  is  when~the  waters 
are  rising ;  and  ebb  tide,  when  they  are  falling.  The  highest 
and  lowest  points  to  which  they  go  are  called,  respectively,  high 
and  low  tides.  The  tides  ebb  and  flow  twice  every  twenty-four 
hours — i.  e.,  we  have  two  flood  and  two  ebb  tides  in  that  time. 

jycle  of  oscillation?  Its  probable  limits?  What  conclusion  from  this  oscillation  of  the 
ecliptic?  595.  By  what  meihod  do  astronomers  determine  the  obliquity  of  the  ecliptic? 
590.  Wbit  are  tides?  Flood  and  ebb  tides?  High  and  low?  Uow  often  do  'hey  c-bo 
and  flow  ? 


PHILOSOPHY    OF    THE    TIDES. 


281 


597.  The  tides  are  not  uniform,  either  as  to  time  or  amount. 
They  occur  about  50  minutes  later  every  day   (as  we  shall 
explain  hereafter),  and  sometimes  rise  much  higher  and  sink 
much  lower  than  the  average.     These  extraordinary  high  and 
low  tides  are  called,  respectively,  spring  and  map  tides. 

598.  The  cause  of  the  tides  is  the  attraction  of  the  Sun  and 
Moon  upon  the  water  of  the  ocean.     But  for  this  foreign  influ- 
ence, as  we  may  call  it,  the  waters  having  found  their  proper 
level,  would  cease  to  heave  and  swell,  as  they  now      Nrt  TinK 
do,  from  ocean  to  ocean,  and  would  remain  calm 

and  undisturbed,  save  by  their  own  inhabitants  and 
the  winds  of  heaven,  from  age  to  age. 

In  this  figure,  the  Earth  is  represented  as  surrounded  by  water,  in  a 
state  of  rest  or  equilibrium,  as  it  would  be  were  it  not  acted  upon  by 
the  Sun  and  Moon. 

599.  To  most  minds,  it  would  seem  that  the  natural  effect  ot 
the  Moon's  attraction  would  be  to  produce  a  single  tide-wave 
on  the  side  of  the  Earth  toward  the  Moon.     It  is  easy,  there- 
fore, for  students  to  conceive  how  the  Moon  can  produce  one 
flood  and  one  ebb  tide  in  twenty  four  hours. 

In  this  cut,  the  Moon  is  shown  at  a  distance  above  the  Earth,  and  ONB  TIDE-WAVK. 
attracting  the  waters  of  the  ocean,  so  as  to  produce  a  high  tide  at  A. 
But  as  the  moon  makes  her  apparent  westward  revolution  around  the 
Earth  but  once  a  day,  the  simple  rising  of  a  flood  tide  on  the  side  of  the 
Earth  toward  the  moon,  would  give  give  us  but  one  flood  and  one  ebb 
tide  in  twenty-four  hours ;  whereas  it  is  known  that  we  have  two  of 
each. 

"  The  tides,"  says  Dr.  Herschel,  "  are  a  subject  on  which  many  per- 
sons find  a  strange  difficulty  of  conception.  That  the  Moon  by  her 
attraction,  should  heap  up  the  waters  of  the  ocean  under  her,  seems  to 
many  persons  very  natural.  That  the  same  cause  should,  at  the  same 
time,  heap  them  up  on  the  opposite  side  of  the  Earth  (viz.,  at  B  in  the 
figure),  seems  to  many  palpably  absurd.  Yet  nothing  is  more  true." 

600.  Instead  of  a  single  tide-wave  upon  the  waters  Two  TIDE- WAVER. 
of  the  globe,  directly  under  the  Moon,  it  is  found 

that  on  the  side  of  the  Earth  directly  opposite, 
there  is  another  hign  tide  ;  and  that  half-way 
between  these  two  high  tides  are  two  low  tides. 
These  four  tides,  Viz.,  two  high  and  two  low, 
traverse  the  ocean  from  east  to  west  every  day, 
which  accounts  for  both  a  flood  and  an  ebb  tide 
every  twelve  hours. 

597  Are  the  tides  uniform?  What  variation  of  time?  As  to  amount?  What  are 
these  extraordinary  high  and  low  tides  called?  598.  The  cause  of  tides?  How  but 
for  this  influence  ?  599.  What  most  obvious  effect  of  the  Moon's  attraction  ?  Substance 
of  note?  Remark  of  Dr.  Herschel?  600.  How  many  tide-waves  are  there  on  the 
globe,  and  how  situated  ? 


€ 


ASTRONOMY. 

In  this  cut,  we  have  a  representation  of  the  tide-waves  as  they  actually  exist,  exocot 
that  their  height,  as  compared  with  the  magnitude  of  the  Earth,  is  vastly  too  great. 
It  is  designedly  exaggerated,  the  better  to  illustrate  the  principle  under  consideration. 
While  the  Moon  at  A  attracts  the  waters  of  the  ocean,  and  produces  a  high  tide  at  B, 
we  see  another  high  tide  at  C  on  the  opposite  side  of  the  globe.  At  the  same  time  it  is 
low  tide  at  D  and  £. 

601.  The  principal  cause  of  the  tide-wave  on  the  side  of  the 
Earth  opposite  the  Moon  is  the  difference,  of  the  Moon's  attrac- 
tion on  different  sides  of  the  Earth. 

If  the  student  well  understands  the  subject  of  gravitation,  he  will  easily  perceive 
how  a  difference  of  attraction,  as  above  described,  would  tend  to  produce  an  elongation 
of  the  huge  drop  of  water  called  the  Earth.  The  diameter  of  the  Earth  amounts  to  about 
J_th  of  the  Moon's  distance ;  so  that,  by  the  rule  (558),  the  difference  in  her  attraction 
on  the  side  of  the  Earth  toward  her,  and  the  opposite  side,  would  be  about  y^th.  The 
attraction  being  stronger  at  B  (in  the  last  cut)  than  at  the  Earth's  center,  and  stronger 
at  her  center  than  at  C,  would  tend  to  separate  these  three  portions  of  the  globe,  giving 
the  waters  an  elongated  form,  aud  producing  two  opposite  tide-waves,  as  shown  in 
the  cut. 

602.  A  secondary  cause  of  the  tide-wave  on  the  side  of  the 
Earth  opposite  the  Moon,  is  the  revolution  of  the  Earth  around 
the  common  center  of  gravity  between  the  Earth  and  Moon, 
thereby  generating  an  increased  centrifugal  force  on  that  side 
of  the  Earth. 

The  center  of  gravity  between  the  Earth  and  Moon  is  the  point  where  they  would 
exactly  balance  each  other,  if  connected  by"  a  rod,  and  poised  upon  a  fulcrum. 


CKNTEB  OF  GRAVITY  BETWEEN  THE  EARTH  AND  MOON. 


Moon. 

— o 


This  point  which,  according  to  Ferguson,  is  about  6000  miles  from  the  Earth's  center, 
la  represented  at  A  in  the  above,  and  also  in  the  next  cut 

SECONDARY   CAUSE   OF   HIGH   TIDE  OPPOSITE   THE  MOON. 


The  point  A  represents  the  center  of  gravity  between  the  Earth  and  Moon  ;  and  as  it 
lj  tnis  point  which  traces  the  regular  curve  of  the  Earth's  orbit,  it  is  represented  in  the 
arc  of  that  orbit,  while  the  Earth's  center  is  6000  miles  one  side  of  it.  Now,  the  law  of 
gravitation  requires  that  while  both  the  Moon  and  Earth  revolve  around  the  Sun,  they 
ehould  also  revolve  around  the  common  center  of  gravity  between  them,  or  around  tho 
point  A.  This  would  give  the  Earth  a  third  revolution,  in  addition  to  that  around  thf 

601.  State  the  principal  cause  of  the  wave  opposite  the  Moon?  Demonstrate  by  dia- 
gram. 602.  What  other  cause  operates  with  the  one  just  stated  to  pro<l  ice  the  tide- 
wave  opposite  the  Moon  ?  What  is  the  center  of  gravity  between  the  Earth  and  the 
Moon  ?  Where  is  it  situated  ?  Illustrate  the  operation  of  this  secondary  cause. 


PHILOSOPHY    OF    T'lE    TIDES.  283 

Sun  and  on  her  axis.     The  small  circles  show  her  path  around  the  center  of  gravity,  and 
the  arrows  her  direction. 

This  motion  of  the  Earth  would  slightly  increase  the  centrifugal  tendency  ai  B,  and 
thus  help  to  raise  the  tide-wave  opposite  the  Moon.  But  as  this  motion  is  slow,  corre- 
sponding with  the  revolution  of  the  Moon  around  the  Earth,  the  centrifugal  force  could 
not  be  greatly  augmented  by  such  a  cause. 

603.  As  the  Moon,  which  is  the  principal  cause  of  the  tides, 
is  revolving  eastward,  and  comes  to  the  meridian  later  and  later 
every  night,  so  the  tides  are  about  50  minutes  later  each  success- 
ive day.     This  makes  the  interval  between  two  successive  high 
tides  12  hours  and  25  minutes     Besides 

this  daily  lagging  with  the  Moon,  the 
highest  point  of  the  tide-wave  is  found 
to  be  about  46°  behind,  or  east  of  the 
Moon,  so  that  high  tide  does  not  , 
occur  till  about  three  hours  after  the 
Moon  has  crossed  the  meridian.  The 
waters  do  not  at  once  yield  to  the  im- 
pulse of  the  Moon's  attraction,  but 
continue  to  rise  after  she  has  passed 
over. 

In  the  cut,  the  Moon  is  on  the  meridian,  but  the  highest  point  of  the  wave  is  at  A,  or 
45°  east  of  the  meridian ;  and  the  corresponding  wave  on  the  opposite  side  at  B  is  equally 
behind. 

604.  The  time  and  character  of  the  tides  are  also  affected  by 
winds,  and  by  the  situation  of  different  places.     Strong  winds 
may  either  retard  or  hasten  the  tides,  or  may  increase  or  diminish 
their  height ;  and  if  a  place  is  situated  on  a  large  bay,  with  but 
a  narrow  opening  into  the  sea,  the  tide  will  be  longer  in  rising, 
as  the  bay  has  to  fill  up  through  a  narrow  gate.     Hence  it  is 
not  usually  high  tide  at  New  York  till  eight  or  nine  hours  after 
the  Moon  has  passed  the  meridian. 

605.  As  both  the  Sun  and  Moon  are  concerned  in  the  produc- 
tion of  tides,  and  yet  are  constantly  changing  their  positions 
with  respect  to  the  earth  and  to  each  other,  it  follows  that  they 
sometimes  act  against  each  other,  and  measurably  neutralize  each 
other's  influence  ;  while  at  other  times  they  combine  their  forces, 
and  mutually  assist  each  other.     In  the  latter  case,  an  unusually 
high  tide  occurs,  called  the  Spring  Tide.     This  happens  both  at 
new  and  full  Moon. 

608.  What  daily  lagging  of  the  tides  ?  Interval  between  two  successive  high  tides  ? 
What  other  lagging?  Cause  of  this  last?  604.  What  modification  of  the  time  and 
character  of  the  tides  ?  605.  Do  the  Sun  and  Moon  always  act  together  in  attracting 
the  waters?  Why  not?  How  affect  each  other's  influence  ?  Effect  on  the  tides ?  What 
t.re  Spring  Tides?  When  do  they  occur?  Illustrate  by  diagram  the  cause  of  spring 
tides,  when  the  Sun  and  Moon  are  in  conjunction. 


284 


ASTRONOMY. 

CAUSK  OF  SPBINO  TIDB3. 


Here  the  Sun  and  Moon,  being  in  conjunction,  unite  their  forces  to  produce  an  extra, 
ordinary  tide.  The  same  effect  follows  when  they  are  in  opposition  ;  so  that  we  have 
two  spring  tides  every  month— namely,  at  new  and  full  Moon. 

If  the  tide-waves  at  A  and  B  are  one-third  higher  at  the  Moon's  quadrature  than  usual, 
those  of  C  and  D  will  be  one-third  lower  than  usual. 

606.  When  the  Moon  is  in  quadrature,  and  her  influence  is 
partly  neutralized  by  the  Sun,  which  now  acts  against  her,  the 
result  is  a  very  low  tide,  called  Neap  Tide. 

SPRING  AND  NEAP  TIDES. 

The  whole  philosophy  of  spring  and 
neap  tides  may  be  illustrated  by  the  an- 
nexed diagram. 

On  the  right  side  of  the  cut,  the  Sun 
and  Moon  are  in  conjunction,  and  unite 
to  produce  a  spring  tide. 

'At  the  first  quarter,  their  attraction 
acts  at  right  angles,  and  the  Sun,  instead 
of  contributing  to  the  lunar  tide-waves, 
detracts  from  it  to  the  amount  of  his 
own  attractive  force.  The  tendency  to 
form  a  tide  of  his  own,  as  represented  in 
the  figure,  reduces  the  Moon's  wave  to 
the  amount  of  one-third. 

At  the  full  Moon,  she  is  in  opposition 
to  the  Sun,  and  their  joint  attraction 
acting  again  in  the  same  line,  tends  to 
elongate  the  fluid  portion  of  the  Earth, 
and  a  second  spring  tide  is  produced. 

Finally,  at  the  third  quarter,  the  Suu 
and  Mtoon  act  against  each  other  again, 
and  the  second  neap  tide  is  the  result. 
Thus  we  have  two  spring  and  two  neap 
tides  during  every  lunation — the  former 
at  the  Moon's  cyzygies,  and  the  latter  at  her  quadratures. 

607.  Although  the  Sun  attracts  the  Earth  much  more  power 
fully,  as  a  whole,  than  the  Moon  does,  still  the  Moon  contributes 
more  than  the  Sim  to  the  production  of  tides.     Their  relative 
influence  is  as  one  to  three.     The  nearness  of  the  Moon  makes 


606.  What  are  Neap  Tides  f  Their  cause  ?  Illustrate  entire  philosophy  by  diagram. 
607.  Comparative  influence  of  Sun  and  Moon  in  the  production  of  tides  ?  Why  Moon1- 
Infiucnce  the  greatest?  Substance  of  note  ?  Demonstration? 


PHILOSOPHY    OF    THE    TIDES. 


285 


the  difference,  of  her  attraction  on  different  sides  of  the  Earth 
much  greater  than  the  difference  of  the  Sun's  attraction  on  dif- 
ferent sides. 

It  must  not  be  forgotten  that  the  tides  are  the  result  not  so  much  of  the  attraction  of 
the  Sun  and  Moon,  as  a  whole,  as  of  the  difference  in  their  attraction  on  different  sides 
of  the  Earth,  caused  by  a  difference  in  the  distance*  of  the  several  parts.  The  attrac- 
tion being  inversely  as  the  square  of  the  distance  (558),  the  influence  of  the  Sun  and 
Moon,  respectively,  must  be  in  the  ratio  of  the  Earth's  diameter  to  their  distances.  Now 

the  difference  in  the  distance  of  two  sides  of  the  Earth  from  the  Moon  is  -o^th  of  the 
Moon's  distance  ;  as  240,000-1-8,000=80  ;  while  the  difference,  as  compared  with  the  dis* 
tance  of  the  Sun,  is  only  TTtYJ  th'  as  95,000,000+8,000=11,875. 


TIDES  AFFECTED  BY  DECLINA- 
TION. 


608.  The  tides  are  subject  to  another  periodic  variation, 
caused  by  the  declination  of  the  Sun  and 
Moon  north  and  south  of  the  equator. 
As  the  tendency  of  the  tide-wave  is  to 
rise  directly  under  the  Sun  and  Moon, 
when  they  are  in  the  south,  as  in  winter, 
or  in  the  north,  as  in  summer,  every 
alternate  tide  is  higher  than  the  interme- 
diate one. 

At  the  time  of  the  equinoxes,  the  Sun  being  over  the 
equator,  and  the  Moon  within  5&°  of  it,  the  crest  of  the 
great  tide-wave  will  be  on  the  equator  ;  but  as  the  Sun 
and  Moon  decline  south  to  A,  one  tide-wave  forms  in  the 
south,  as  at  B,  and  the  opposite  one  in  the  north,  as  at 
C.  If  the  declination  was  north,  as  shown  at  D,  the  order  of  the  tides  would  be  reversed. 
The  following  diagram,  if  carefully  studied,  will  more  fully  illustrate  the  subject  of  tn« 
alternate  high  and  low  tides,  in  high  latitudes,  in  winter  and  summer  : 


ALTERNATE  HIGH  AND  LOW  TIDES. 


let  the  line  A  A  represent  the  plane  of  the  ecliptic,  and  B  B  the  equinoctial.  On  the 
21st  of  June,  the  day  tide-wave  is  north,  and  the  evening  wave  south,  so  that  the  tide 
following  about  three  hours  after  the  Sun  and  Moon,  will  be  higher  than  the  intermediate 
one  at  3  o'clock  in  the  morning. 

On  the  23d  of  December,  the  Sun  and  Moon  being  over  the  southern  tropic,  the 
highest  wave  in  the  southern  hemisphere  will  be  about  8  o'clock  P.  M  ,  and  the  lowest 
about  3  o'clock  A.M. ;  while  at  the  north,  this  order  will  be  reversed.  It  is  on  this 
account  that  in  high  latitudes  every  alternate  tide  is  higher  than  the  intermediate  ones ; 
the  evening  tides  in  summer  exceeding  the  morning  tides,  and  the  morning  tides  in  win- 
ter exceeding  those  of  evening. 

609.  All  spring  and  neap  tides  are  not  alike  as  to  their  eleva 
tion  and  depression.     As  the  distances  of  the  Sun  and  Moon  arc 


608.  What   other  periodic  variations  mentioned?      Explain   cause,   and   illustrate* 
fioy.  Are  all  spring  and  neap  ti']f-s  alike?    By  what  are  they  modified?    Illustrate  ly 

di.-igram. 


5*86 


ASTRONOMY. 


varied,  so  are  the  tides  varied,  especially  by  the  variations  of 
the  Moon. 


VARIATIONS  IN  THE  SPRING  TIDES. 


At  A,  the  Earth  is  in  aphelion,  and  the  Moon  in  apogee.  As  both  the  Sun  and  Moon 
are  at  their  greatest  distances,  the  Earth  is  least  affected  by  their  attraction,  arid  the 
spring  tides  are  proportionately  low. 

A  j  B,  the  Earth  is  in  perihelion,  and  the  Moon  in  perigee;  so  that  both  the  Sun  and 
Moon  exert  their  greatest  influence  upon  our  globe,  and  the  spring  tides  are  highest,  aa 
ehewn  in  the  figure.  In  both  cases,  the  Sun  and  Moon  are  in  conjunction,  but  the  varia- 
tion in  the  distances  of  the  Sun  and  Moon  causes  variations  in  the  spring  tides. 

610.  In  the  open  ocean,  especially  the  Pacific,  the  tide  rises 
and  falls  but  a  few  feet  ;  but  when  pressed  into  narrow  bays 
or   channels,  it  rises   much  higher  than  under   ordinary  cir- 
cumstances. 

The  average  elevation  of  the  tide  at  several  points  on  our  coast  is  as  follows : 

Cumberland,  head  of  the  Bay  of  Fundy 71      feel. 

*   Boston 11^     " 

New  Haven 8       " 

New  York 5        " 

Charleston,  S.  C 6        " 

611.  As  the  great  tide-waves  proceed  from  east  to  west,  they 
are  arrested  by  the   continents,  so  that  the  waters  are   per- 
manently higher  on  their  east  than  on  their  west  sides.     The 
Gulf  of  Mexico  is  20  feet  higher  than  the  Pacific  Ocean,  on  the 
other  side  of  the  Isthmus  ;  and  the  Red  Sea  is  30  feet  higher 
than  the  Mediterranean.     Inland  seas  and  lakes  have  no  per- 
ceptible tides,  because  they  are  too  small,  compared  with  the 
whole  surface  of  the  globe,  to  be  sensibly  affected  by  the  attrac- 
tion of  the  Sun  and  Moon. 

ATMOSPHERICAL   TIDES. 

612.  Air  being  lighter  than  water,  and  the  surface  of  the 
atmosphere  being  nearer  to  the  Moon  than  the  surface  o'  the 
sea,  it  cannot  be  doubted  but  that  the  Moon  raises  much  higner 

610.  Height  of  tides  in  open  seas  ?  How  in  narrow  bays  and  channels  ?  Height  at  dif- 
ferent points  on  our  coast  ?  611.  Direction  of  tide-waves?  What  result?  Instances 
cited?  Have  inland  seas  and  lakes  any  tides?  Why  not  ?  Remarks  respecting  p)u- 
iosophy  of  tides  ?  612  Atmospheric  tides  ? 


TtlE    SEASONS.  287 

tides  in  the  atmosphere  than  in  the  sea.  According  to  Sir 
John  Herschel  these  tides  are,  by  very  delicate  observations, 
rendered  not  only  sensible,  but  measurable. 

Upon  the  supposition  that  there  is  water  on  the  surface  of  the  Moon  of  the  same 
specific  gravity  as  our  own,  we  might  easily  determine  the  height  to  which  the  Earth 
would  raise  a  lunar  tide,  by  the  known  principle,  that  the  attraction  of  one  of  these 
bodies  on  the  other's  surface  is  directly  as  its  quantity  of  matter,  and  inversely  as  its 
diameter.  By  making  the  calculation,  we  shall  find  the  attractive  power  of  the  Karth 
upon  the  Moon  to  be  21,777  times  greater  than  that  of  the  Moon  upon  the  Earth. 

613.  We  have  thus  stated  the  principal  facts  connected  with 
this  complicated  phenomenon,  and  the  causes  to  which  they  are 
generally  attributed.  And  yet  it  is  not  certain  that  the  philoso- 
phy of  tides  is  to  this  day  fully  understood.  La  Place,  the  great 
French  mathematician  and  astronomer,  pronounced  it  one  of  the 
most  difficult  problems  in  the  whole  range  of  celestial  mechanics. 
It  is  probable  that  the  atmosphere  of  our  globe  has  its  tides,  as 
well  as  the  waters  j,  but  we  have  no  means,  as  yet,  for  definitely 
ascertaining  the  fact 


CHAPTER  XIY. 

THE  SEASONS— DIFFERENT  LENGTHS  OF  THE  DAYS  AND 
NIGHTS. 

614.  THE  vicissitudes  of  the  seasons,  and  the  unequal  lengths 
of  the  days  and  nights,  are  occasioned  by  the  annual  revolution 
of  the  Earth  around  the  Sun,  with  its  axis  inclined  to  the  plane 
of  its  orbit.  The  temperature  of  any  part  of  the  Earth's  sur- 
face depends  mainly,  if  not  entirely,  upon  its  exposure  to  the 
Sun's  rays. 

INCLINATION   OF  THE   EABTfl's   AXIS  TO  THE  PLANK  OF  THE  ECLIPTIC. 

THE    ECLIPTIC  /5K£ 


615.  Whenever  the  Sun  is  above  the  horizon  of  any  place, 
that  place  is  receiving  heat  ;  when  the  Sun  is  below  the  horizon 
it  is  parting  with  it,  by  a  process  which  is  called  radiation.  The 
quantities  of  heat  thus  received  and  imparted  in  the  course  of 
the  year,  must  balance  each  other  at  every  place,  or  the  equi- 

(H8.  Is  it  certain  that  this  subject  is  even  yet  well  understood  ?  Remark  of  Laplace? 
614.  Cause  of  the  seasons,  and  the  unequal  length  cf  the  days  and  nights?  Temperat'irc 
of  the  Earth  ?  615.  When  does  any  place  gain  heat,  and  when  lose  ?  Upon  what  doet 


28S 


ASTRONOM*. 


librium  of  temperature  would  not  be  supported.  Whenever  tne 
Sun  remains  more  than  twelve  hours  above  the  horizon  of  any 
place,  and  less  beneath,  the  general  temperature  of  that  place 
will  be  above  the  mean  state  ;  when  the  reverse  takes  place,  the 
temperature,  for  the  same  reason,  will  be  below  the  mean  state. 
Kow,  the  continuance  of  the  Sun  above  the  horizon  of  any  place, 
depends  entirely  upon  his  declination,  or  altitude  at  noon. 

616.  About  the  20th  of  March,  when  the  Sun  is  in  the  ver- 
nal equinox,  and  consequently  has  no  declination,  lie  rises  at  six 
in  the  morning  and  sets  at  six  in  the  evening  ;  the  day  and  night 
are  then  equal,  and  as  the  Sun  continues  as  long  above  our 
horizon  as  below  it,  his  influence  must  be  nearly  the  same  at  the 
same  latitudes,  in  both  hemispheres. 

From  the  20th  of  March  to  the  21st  of  June,  the  days  grow 
longer,  and  the  nights  shorter,  in  the  northern  hemisphere  ;  the 
temperature  increases,  and  we  pass  from  spring  to  midsummer  ; 
while  the  reverse  of  this  takes  place  in  the  southern  hemisphere. 

From  the  21st  of  June  to  the  23d  of  September,  the  days 
and  nights  again  approach  to  equality,  and  the  excess  of  tem- 
perature in  the  northern  hemisphere  abote the  mean  state,  grows 
less,  as  also  its  defect  in  the  southein  ;  so  that,  when  the  Sun 
arrives  at  the  autumnal  equinox,  the  mean  temperature  is  again 
restored. 


617.  From  the  23d  of 
September  until  the  21st  of 
December,  our  nights  grow 
longer  and  the  days  shorter, 
and  the  cold  increases  as 
before  it  diminished,  while 
we  pass  from  autumn  to 
mid-winter,  in  the  northern 
hemisphere,  and  the  inhabit- F 
ants  of  the  southern  hemi- 
sphere from  spring  to  mid- 
summer. 

From  the  21st  of  Dec. 
to  the  20th  of  March,  the 
cold  relaxes  as  the  days  grow 
longer,  and  we  pass  from 


CAUSE   OF  THE  SEASONS. 
B 


the  length  of  the  days  depend?  616.  How  about  the  20th  of  March?  From  March 
520th  to  June  21st?  From  June  21st  to  September  23d  ?  617.  From  September  23d  to 
I/uvsmber  21st  ?  From  December  21st  to  March  20th?  II(  w  with  the  seasons  in  the 


THE    SEASONS.  289 

the  dreariness  of  winter  to  the  mildness  of  spring,  when  the 
seasons  are  completed,  and  the  mean  temperature  is  again 
restored.  The  same  vicissitudes  transpire,  at  the  same  time,  in 
the  southern  hemisphere,  but  in  a  contrary  order.  Thus  are 
produced  the  four  seasons  of  the  year. 

In  the  preceding  cut,  the  Earth  is  shown  in  her  orbit,  with  her  axis  inclined  23J$e ;  the 
North  Pole  being  towards  the  eye  of  the  student.  At  A  and  B  the  Sun  shines  from  pole 
to  pole,  and  the  days  and  nights  are  equal  in  both  hemispheres.  On  the  right,  the  North 
Pole  is  in  the  light,  and  we  have  summer  in  the  northern  hemisphere.  On  the  left,  the 
reverse  is  the  case.  And  the  gradual  shortening  or  lengthening  of  the  days,  and  the 
change  of  temperature,  are  produced  by  the  passage  of  the  Earth  from  one  point  to 
another,  with  her  axis  thus  inclined. 

618.  But  I  have  stated  not  the  only,  nor,  perhaps,  the  most 
efficient  cause  in  producing  the  heat  of  summer  and  the  cold  of 
winter.  If,  to  the  inhabitants  of  the  equator,  the  Sun  were  to 
remain  16  hours  below  their  horizon,  and  only  8  hours  above  it, 
for  every  day  of  the  year,  it  is  certain  they  would  never  expe- 
rience the  rigors  of  our  winter  ;  since  it  can  be  demonstrated, 
that  as  much  heat  falls  upon  the  same  area  from  a  vertical  Sun 
in  8  hours,  as  would  fall  from  him,  at  an  angle  of  60°,  in  16 
hours. 

Now,  as  the  Sun's  rays  fall  most  obliquely  when  the  days  are 
shortest,  and  most  directly  when  the  days  are  Longest,  these  two 
causes — namely,  the  duration  and  intensity  of  the  solar  heat, 
together,  produce  the  temperature  of  the  different  seasons.  The 
reason  why  we  have  not  the  hottest  temperature  when  the  days 
are  longest,  and  the  coldest  temperature  when  the  days  are 
shortest,  but  in  each  case  about  a  mouth  afterwards,  appears  to 
be,  that  a  body  once  heated,  does  not  grow  cold  instantaneously, 
but  gradually,  and  so  of  the  contrary.  Hence,  as  long  as  more 
heat  comes  from  the  Sun  by  day  than  is  lost  by  night,  the  heat 
will  increase,  and  vice  vcrsd. 

BEGINNING  AND  LENGTH  OF  THB  SEASONS. 


Sun  enters  \3  (Winter  begins 

1849,  December  21, 

11. 

7 

Ml. 

25 

46  M.  T.  Wash. 

u         u 

T   (Spring        " 

1860,  March 

20, 

8 

50 

38 

" 

((          1C 

C5  (Summer     " 

"      June 

21, 

G 

3 

9 

11             tC 

u         i( 

=£=  (Autumn     " 

"       Sept. 

22, 

19 

68 

21 

U              (1 

tl        u 

\3  (Winter       " 

"       December  21, 

18 

'21 

57 

u          it 

outhern  hemisphere  ?       618.  Is  the  simple  fact  that  a  place  if  enlightened  by  the  Sun,  a 
ufficient  cause  for  its  being  warm?     What  circumstance  determines  the  intensity  o'  the 

Bun's  raya?     Why,  then,  is  it  not  warmest  during  the  longest  days,  and  on  the  cona-iiy 

coldest  during  the  shortest  days  ?    How  long  will  heat  increase  ? 


290  ASTRONOMY. 

Sun  in  the  Winter  Signs          ...        .  89    1  30  52 

"      "      Spring 92  21    6  81 

"      "      Summer                  .        .        .        .  93  13  55  22 

"      «'      Autumn 89  17  23  26 

"  north  of  Equator  (Spring  and  Summer)  186  11    1  53 

"  south           "         (Winter  and  Autumn)  178185418 

Longest  north  of  the  Equator          .        .         7  16    7  85 
Length  of  the  tropical  year  beginning  at  ) 

the  winter  solstice  1849,  and  ending  at  V      ?65    5  56  11 

the  winter  solstice  1850.  ) 

Mean  or  average  length  of  the  tropical  year,    865    5  48  48 

619.  The  north  pole  of  the  Earth  is  denominated  the  ekvaled 
pole,  because  it  is  always  about  23£°  above  a  perpendicular  to 
the  plane  of  the  ecliptic,  and  the  south  pole  is  denominated  the 
depressed  pole,  because  it  is  about  the  same  distance  below  such 
perpendicular. 

As  the  Sun  cannot  shine  on  more  than  one-half  the  Earth's  surface  at  a  time,  it  is 
plain,  that  when  the  Earth  is  moving  through  that  portion  of  its  orbit  which  lies  above 
the  Sun,  the  elevated  pole  is  in  the  dark.  This  requires  six  months,  that  is,  until  the 
Earth  arrives  at  the  equinox,  when  the  elevated  pole  emerges  into  the  light,  and  the 
depressed  pole  is  turned  away  from  the  Sun  for  the  same  period.  Consequently,  there 
are  six  months  day  and  six  months  night,  alternately,  at  the  poles. 

620.  When  the  Sun  appears  to  us  to  be  in  one  part  of  the 
ecliptic,  the  Earth,  as  seen  from  the  Sun,  appears  in  the  point 
diametrically  opposite.     Thus,  when  the  Sun  appears  in  the  ver- 
nal equinox  at  the  first  point  of  Aries,  the  Earth  is  actually  in 
the  opposite  equinox  at  Libra.     The  days  and  nights  are  then 
equal  all  over  the  world.     (See  the  cut,  pages  288  and  292.) 

As  the  Sun  appears  to  move  up  from  the  vernal  equinox  to  the  summer  solstice,  the 
Earth  actually  moves  from  the  autumnal  equinox  down  to  the  winter  solstice.  The  days 
now  lengthen  in  the  northern  hemisphere,  and  shorten  in  the  southern.  The  Sun  is  now 
over  the  north  pole,  where  it  is  mid-day,  and  opposite  the  south  pole,  where  it  is  midnight. 

As  the  Sun  descends  from  the  summer  solstice  towards  the  autumnal  equinox,  the  Earth 
ascends  from  the  winter  solstice  towards  the  vernal  equinox.  The  summer  days  in  the 
northern  hemisphere  having  waxed  shorter  and  shorter,  now  become  again  of  equal 
length  in  both  hemispheres. 

621.  While  the  Sun  apears  to  move  from  the  autumnal  equi- 
nox down  to  the  winter  solstice,  the  Earth  passes  up  from  the 
vernal  equinox  to  the  summer  solstice  ;  the  south  pole  comes 
into  the  light,  the  winter  days  continually  shorten  in  the  northern 
hemisphere,  and  the  summer  days  as  regularly  increase  in  length 
in  the  southern  hemisphere. 

While  the  Sun  appears  again  to  ascend  from  its  winte^  solstice 
to  the  vernal  equinox,  the  Earth  descends  from  the  Summer 
solstice  to  the  autumnal  equinox.  The  summer  days  now  shorten 

619.  Which  is  the  elevated  pole,  and  why?  The  depressed,  and  why?  How  are  the 
seasons  produced?  620.  How  are  the  Earth  and  Sun  situated  in  the  ecliptic,  with 
reference  to  each  other?  What  said  of  the  Sun's  apparent  motion  around  the  zodiac i 
621.  What  further  description  of  the  Sun's  apparent  progress? 


THE    SEASONS.  1291 

in  the  southern  hemisphere,  and  the  winter  days  lengthen  in  the 
northern  hemisphere. 

622.  When  the  Sun  passes  the  vernal  equinox,  it  rises  to  the 
arctic  or  elevated  pole,  and  sets  to  the  antarctic  pole.     When 
the  Sun  arrives  at  the  summer  solstice,  it  is  noon  at  the  north 
pole,  and  midnight  at  the  south  pole.     When  the  Sun  passes  the 
autumnal  equinox,  it  sets  to  the  north  pole,  and  rises  to  the 
south  pole.     When  the  Sun  arrives  at  the  winter  solstice,  it  is 
midnight  at  the  north  pole,  and  noon  at  the  south  pole  ;  and 
when  the  Sun  comes  again  to  the  vernal  equinox,  it  closes  the 
day  at  the  south  pole,  and  lights  up  the  morning  at  the  north 
pole. 

There  would,  therefore,  be  186£  days  during  which  the  Sun 
would  not  set  at  the  north  pole,  and  an  equal  time  during  which 
he  would  not  rise  at  the  south  pole  ;  and  17  8|-  days  in  which  he 
would  not  set  at  the  south  pole,  nor  rise  at  the  north  pole. 

623.  At  the  arctic  circle,  23°  2t£'  from  the  pole,  the  longest 
day  is  24  hours,  and  goes  on  increasing  as  you  approach  the 
pole.     In  latitude  67°  18'  it  is  30  days  ;  in  lat.  69°  30'  it  is  60 
days,  &c.     The  same  takes  place  between  the  antarctic  circle 
and  the  south  pole,  with  the  exception,  that  the  day  in  the  same 
latitude  south  is  a  little  shorter,  since  the  Sun  is  not  so  long 
south  of  the  equator,  as  at  the  north  of  it.     In  this  estimate  no 
account  is  taken  of  the  refraction  of  the  atmosphere,  which,  as 
we  shall  see  hereafter,  increases  the  length  of  the  day,  by  mak- 
ing the  Sun  appear  more  elevated  above  the  horizon  than  it 
really  is.     All  these  apparent  motions  of  the  Sun  are  due  to  the 
inclination  of  the  Earth's  axis  (or  the  obliquity  of  the  ecliptic), 
and  her  revolution  around  the  Sun. 

The  following  cut  represents  the  inclination  of  the  Earth's  axis  to  its  orbit  in  every 
one  of  the  twelve  signs  of  the  zodiac,  and  consequently  for  each  month  in  the  year. 
It  is  such  a  view  as  a  beholder  would  have,  situated  in  the  north  pole  of  the  ecliptic,  at 
some  distance  from  it,  and  consequently,  is  a  perpendicular  view,  the  north  pole  of  the 
Earth  being  towards  us.  The  Sun  enters  the  sign  Aries,  or  the  vernal  equinox,  on  the 
20th  of  March,  when  the  Earth  enters  Libra,  and  when  her  axis  inclines  neither  towards 
the  Sun,  nor  from  it,  but  stands  exactly  sideways  to  it;  so  that  the  Sun  then  shines 
equally  upon  the  Earth  from  pole  to  pole,  and  the  days  and  nights  are  everywhere  equal. 
This  is  the  beginning  of  the  astronomical  year;  it  is  also  the  beginning  of  day  at  the 
north  pole,  which  is  just  coming  into  light  and  the  end  of  day  at  the  south  pole,  which 
is  just  going  into  darkness. 

By  the  Earth's  orbitual  progress,  the  Sun  appears  to  enter  the  second  sign,  Taurus, 
on  the  20th  of  April,  when  the  north  pole  has  sensibly  advanced  into  the  light,  while  the 
Bouth  pole  has  been  declining  from  it;  whereby  the  days  become  longer  than  the  nights 
In  the  northern  hemisphere,  and  shorter  in  the  southern. 

On  the  21st  of  May,  the  Sun  appears  to  enter  the  sign  Gemini,  when  the  north  pole 

622.  How  are  the  light  and  darkness  of  the  poles  affected  by  the  Sun's  apparent  motion  ? 
623.  What  said  of  the  length  of  the  days  within  the  arctic  circle  ?  In  latitude  67°  18'  ? 
In  latitude  69-  80'  ?  How  at  the  other  pole  ?  To  what  are  these  various  apoarenl 
(notions  of  the  Sun  really  due  ? 

U.G.  13 


292 


ASTRONOMY. 


has  advanced  considera-  PHILOSOPHY  OP  THE  SEASONS.* 

bly  further  into  the  light, 

while  the  south  pole  has 

proportionally     declined 

from    It;     the    summer 

days    are    now    waxing 

longer   in  the    northern 

hemisphere,     and      the 

nights  shorter. 

The  21st  of  June,  when 
the  Sun  enters  the  sign 
Cancer,  is  the  first  day 
of  summer  in  the  astro- 
nomical year,  and  the 
longest  day  in  the  north- 
ern hemisphere.  The 
north  pole  now  has  its 
jreatest  inclination  to 
the  Sun,  the  light  of 
which,  as  is  shown  by 
the  boundary  of  light  and 
darkness,  in  the  figure, 
extends  to  the  utmost 
verge  of  the  Arctic  Cir- 
cle ;  the  whole  of  which 
is  included  in  the  enlight^ 
ened  hemisphere  of  the 
Earth,  and  enjoys,  at 
this  season,  constant  day 
during  the  complete  revo- 
lution of  the  Earth  on  its 
axis.  The  whole  of  the  Northern  Frigid  Zone  is  now  in  the  circle  of  perpetual  illumi- 
nation. 

On  the  23d  of  July,  the  Sun  enters  the  sign  Leo,  and  as  the  line  of  the  Earth's  axis  always 
continues  parallel  to  itself,  the  boundary  of  light  and  darkness  begins  to  approach  nearer 
to  the  poles,  and  the  length  of  the  day  in  the  northern  hemisphere,  which  had  arrived 
at  its  maximum,  begins  gradually  to  decreose.  On  the  23d  of  August,  the  Sun  enters  the 
sign  Virgo,  increasing  the  appearances  mentioned  in  Leo. 

On  the  23d  of  September,  the  Sun  enters  Libra,  the  first  of  the  autumnal  signs,  when 
the  Earth's  axis  having  the  same  inclination  as  it  had  in  the  opposite  sign,  Aries,  is 
turned  neither  from  the  Sun,  nor  towards  it,  hut  obliquely  to  it,  so  that  the  Sun  again 
now  shines  equally  upon  the  whole  of  the  Earth's  surface  from  pole  to  pole.  The  days 
and  nights  are  once  more  of  equal  length,  throughout  the  world. 

On  the  23d  of  October,  the  Sun  enters  the  sign  Scorpio ;  the  days  visibly  decrease 
in  length  in  the  northern  hemisphere,  and  increase  in  the  southern. 

On  the  22d  of  November  the  Sun  enters  the  sign  Sagittarius,  the  last  of  the  autumnal 
signs,  at  which  time  the  boundary  of  light  and  darkness  is  at  a  considerable  distance 
from  the  north  pole,  while  the  south  pole  has  proportionally  advanced  into  the  light;  the 
length  of  the  day  continues  to  increase  in  the  southern  hemisphere,  and  to  decrease  in 
the  northern. 

On  the  21st  of  December,  which  is  the  period  of  the  winter  solstice,  the  Sun  enters  the 
sign  Capricorn.  At  this  time,  the  north  pole  of  the  Earth's  axis  is  turned  from  the 
Sun,  into  perpetual  darkness;  while  the  south  pole,  in  its  turn,  is  brought  into  the  light 
of  the  Sun,  whereby  the  whole  Antarctic  region  comes  into  the  circle  of  perpetual  illumi- 
nation. It  is  now  that  the  southern  hemisphere  enjoys  all  those  advantages  with  which 
the  northern  hemisphere  was  favored  on  the  21st  of  June ;  while  the  northern  hemi- 
sphere, in  its  turn,  undergoes  the  dreariness  of  winter,  with  short  days  and  long 
nights. 


*  This  diagram  and  the  accompanying  explanations  should  be  carefully  studied  till 
'^ey  are  thoroughly  understood  by  the  learner.  The  cause  of  the  seasons  and  of  the 
uuv'aual  lengths  of  the  days  and  nights,  is  a  matter  of  which  no  professedly  educated 
person  ought  to  be  ignorant,  or  to  entertain  confused  and  indefinite  notions.  By  all 
inenns  iet  this  point  be  studied  till  the  student  can  tell  the  cause  of  every  particular  phe- 
nomenon of  the  seasons  and  the  length  of  the  days,  without  any  particular  interr> 
Eution. 


THE  HARVEST  MOON  AND  HORIZONTAL  MOON.     293 

624.  By  carefully  observing  the  figure,  it  may  be  seen  that 
the  orbit  of  the  Earth  is  slightly  elliptical,  that  the  Sun  is  to 
the  left  of  the  center,  and  that  consequently,  the  Earth  is  nearer 
the  San  on  the  21st  of  December,  than  on  the  opposite  side  of 
the  ecliptic,  on  the  21st  of  June.     This  may  seem  strange  to  the 
learner,  that  we  should  have  our  winter  when  nearest  the  Sun, 
and  our  summer  when  most  distant  ;  but  it  must  be  remembered 
that  the  temperature  of  any  particular  part  of  the  Earth  is 
not  so  much  affected  by  the  distance  of  the  Sun,  as  by  the  direct- 
ness or  obliquity  of  his  rays.     Hence,  though  we  are  farther 
from  the  Sun  on  the  21st  of  June  than  on  the  21st  of  December, 
yet,  as  the  north  pole  of  the  Earth  is  turned  more  directly  into 
the  light  at  that  time,  so  that  the  Sun's  rays  strike  her  surface 
less  obliquely  than  in  December,  we  have  a  higher  temperature 
at  that  period,  though  at  a  greater  distance  from  the  Sun. 

625.  The  difference,  however,  between  the  aphelion  and  peri- 
helion distances  of  the  Earth  is  so  slight,  in  comparison  with  the 
whole  distance,  as  scarcely  to  cause  a  perceptible  difference  in  the 
amount  of  light  received  at  her  respective  positions.     The  eccen- 
tricity of  the  Earth's  orbit,  or  the  distance  of  the  Sun  from  its 
center,  is  only  about  1,618,000  miles,  so  that  the  variation  is 
only  3,236,000  miles,  or  about  one-thirtieth  of  the  mean  distance. 
The  true  orbit  of  the  Earth  could  not  be  distinguished  from  a 
circle. 

The  only  effect  of  the  eccentricity  of  the  Earth's  orbit  upon  her  temperature  is,  that 
she  has  probably  a  greater  degree  of  heat,  during  summer  in  the  southern  hemisphere, 
when  the  Earth  is  at  her  perihelion,  than  we  ever  have  at  the  north  iu  the  same  lati- 
tude. But  this  difference  must  be  very  slight,  if  indeed  it  is  at  all  perceptible. 


CHAPTER   XY. 
THE  HAKVEST  MOON  AND  HORIZONTAL  MOON, 

626.  THE  daily  progress  of  the  Moon  in  her  orbit,  from  west  to 
east,  causes  her  to  rise,  at  a  mean  rate,  48  minutes  and  44 
seconds  later  every  day  than  on  the  preceding.  But  in  places 
of  considerable  latitude,  a  remarkable  deviation  from  this  rule 

624.  What  said  of  the  form  of  the  Earth's  orbit  ?  When  arc  we  nearest  the  Sun  \ 
Why  is  it  not  then  the  warmest  in  the  United  States?  625.  What  is  the  amount  of  th« 
Earth's  variation  in  distance  from  the  Sun  ?  What  effect  upon  the  light  and  heat  of  the 
Earth  If  626.  Subject  of  this  chapter?  Mean  rate  of  the  Moon's  daily  delay  \a  Hairy 


294  ASTRONOMf. 

takes  place,  especially  about  the  time  of  Harvest,  when  the  full 
Moon  rises  to  us  for  several  nights  together,  only  from  18  to  25 
minutes  later  in  one  day,  than  on  that  immediately  preceding. 
From  the  benefit  which  her  light  affords,  in  lengthening  out  the 
day,  when  the  husbandmen  are  gathering  in  the  fruits  of  the 
Earth,  the  full  Moon,  under  these  circumstances,  has  acquired 
the  name  of  Harvest  Moon. 

It  is  believed  that  this  fact  was  observed  by  persons  engaged  in  agriculture,  at  a  much 
earlier  period  than  that  in  which  it  was  noticed  by  astronomers.  The  former  ascribed  it 
to  the  goodness  of  the  Deity ;  not  doubting  but  that  he  had  so  ordered  it  for  their  advan- 
tage. 

621.  About  the  equator,  the  Moon  rises  throughout  the  year 
with  nearly  the  equal  intervals  of  48f  minutes  ;  and  there  the 
harvest  Moon  is  unknown.  At  the  polar  circles,  the  autumnal 
full  Moon,  from  her  first  to  her  third  quarter,  rises  as  the  Sun 
sets  ;  and  at  the  poles,  where  the  Sun  is  absent  during  one-half 
of  the  year,  the  winter  full  Moons,  from  the  first  to  the  third 
quarter,  shine  constantly  without  setting. 

By  this,  it  is  not  meant  that  the  Moon  continues  futt  from  her  first  to  her  third  quar- 
ter ;  but  that  she  never  sets  to  the  North  Polar  regions,  when,  at  this  season  of  the  year, 
she  is  within  90*  of  that  point  in  her  orbit,  where  she  is  at  her  full.  In  other  words,  as 
the  Sun  illumines  the  south  pole  during  one-half  of  its  yearly  revolution,  so  the  Moon, 
being  opposite  to  the  Sun  at  her  full,  must  illumine  the  opposite  pole,  during  half  of  her 
revolution  about  the  Earth.  The  phenomenon  of  the  Harvest  Moon  may  be  thus  exem- 
plified by  means  of  the  globe. 

Rectify  the  globe  to  the  latitude  of  the  place,  put  a  patch  or  piece  of  wafer  in  the  eclip- 
tic, on  the  point  Aries,  and  mark  every  12*  preceding  and  following  that  point,  to  the 
number  often  or  twelve  marks  on  each  side  of  it;  bring  the  equinoctial  point  marked  by 
the  wafer  to  the  eastern  edge  of  the  horizon,  and  set  the  index  to  12 ;  turn  the  globe 
westward  till  the  other  marks  successively  come  to  the  horixon,  and  observe  the  hours 
passed  over  by  the  index ;  the  intervals  of  time  between  the  marks  coming  to  the  horizon, 
will  show  the  diurnal  difference  of  time  between  the  Moon's  rising.  If  these  marks  be 
Drought  to  the  western  edge  of  the  horizon  in  the  same  manner,  it  will  show  the  diurnal 
difference  between  the  Moon's  setting. 

From  this  problem  it  will  also  appear,  that,  when  there  is  the  least  difference  between 
the  times  of  the  Moon's  rising,  there  will  be  the  greatest  difference  between  the  tunes  of 
her  setting,  and  the  contrary. 

The  reason  why  you  mark  every  12"  is,  that  the  Moon  gains  12*  11'  on  the  apparent 
course  of  the  Sun  every  day,  and  these  marks  serve  to  denote  the  place  of  the  Moon 
from  day  to  day.  It  is  true,  this  process  supposes  that  the  Moon  revolves  in  the  plane 
of  the  ecliptic,  which  is  not  the  case ;  yet  her  orbit  so  nearly  coincides  with  the  ecliptic 
(differing  only  5°  9'  from  it),  that  they  may,  for  the  convenience  of  illustration,  be  con- 
sidered as  coinciding ;  that  is,  we  may  take  the  ecliptic  for  the  representative  of  the 
Moon's  orbit. 

628.  The  different  lengths  of  the  lunar  night,  at  different  lati- 
tudes, is  owing  to  the  different  angles  made  by  the  horizon  and 
different  parts  of  the  Moon's  orbit  ;  or,  in  other  words,  by  the 

What  remarkable  deviation?  What  is  the  Moon  then  called,  and  why?  How  anciently 
was  this  phenomenon  observed?  To  what  attributed?  627.  Is  the  Harvest  Moon 
known  at  the  equator?  How  at  the  Polar  circles  ?  At  the  poles?  Does  she  there  exhi- 
bit her  usual  phases  ?  Can  you  illustrate  the  phenomenon  of  the  Harvest  Moon  by  u 
globe?  628.  To  what  is  the  different  lengths  of  the  lunar  nights  attributable? 


THE  HARVEST  MOON  AND  HORIZONTAL  MOON.     295 

Moon's  orbit  lying  sometimes  more  oblique  to  the  horizon  than 
at  others. 

In  the  latitude  of  London,  for  example,  as  much  of  the  ecliptic  rises  ab  •mt  Pisces  an»l 
Aries  in  two  hours  as  the  Moon  goes  through  in  six  days  ;  therefore,  while  the  Moon  is  in 
these  signs,  she  differs  but  two  hours  in  rising  for  six  days  together ;  that  is,  one  day 
with  another,  she  rises  about  20  minutes  later  every  day  than  on  the  preceding. 

629.  The  parts  or  signs  of  the  ecliptic  which  rise  with  the 
smallest  angles,  set  with  the  greatest ;  and  those  which  rise  with 
the  greatest,  set  with  the  least.     And  whenever  this  angle  is 
least,  a  greater  portion  of  the  ecliptic  rises  in  equal  times  than 
when  the  angle  is  larger.     Therefore,  when  the  Moon  is  in  those 
signs  which  rise  or  set  with  the  smallest  angles,  she  rises  or  sets 
with  the  least  difference  of  time  ;  but  when  she  is  in  those  signs 
which  rise  or  set  with  the  greatest  angles,  she  rises  or  sets  with 
the  greatest  difference  of  time. 

Let  the  globe,  for  example,  be  rectified  to  the  latitude  of  New  York,  40'  42'  40',  with 
Cancer  on  tho  meridian,  and  Libra  rising  in  the  east.  In  this  position,  the  ecliptic  has  a 
high  elevation,  making  an  angle  with  the  horizon  of  72j£e. 

But  let  the  globe  be  turned  half  round  on  its  axis,  till  Capricorn  comes  to  the  meridian, 
and  Aries  rises  in  the  east,  then  the  ecliptic  will  have  a  low  elevation  above  the  horizon, 
making  an  angle  with  it  of  only  25  J$°.  This  angle  is  47°  less  than  the  former  angle,  and 
is  equal  to  the  distance  between  the  tropics. 

630.  In  northern  latitudes,  the  smallest  angle  made  by  the 
ecliptic  and  horizon  is  when  Aries  rises  ;  at  which  time  Libra 
sets  ;  the  greatest  is,  when  Libra  ijses  and  Aries  sets.     The  eclip- 
tic rises  fastest  about  Aries,  and  slowest  about  Libra.     Though 
Pisces  and  Aries  make  an  angle  of  only  25-^°  with  the  horizon 
when  they  rise,  to  those  who  live  in  the  latitude  of  New  York, 
yet  the  same  signs,  when  they  set,  make  an  angle  of  72^-°.     The 
daily  difference  of  the  Moon's  rising,  when  in  these  signs,  is,  in 
New  England,  about  22  minutes  ;  but  when  she  is  in  the  oppo- 
site signs,  Yirgo  and  Libra,  the  daily  difference  of  her  rising  is 
almost  four  times  as  great,  being  about  one  hour  and  a  quarter 

631.  As  the  Moon  can  never  be  full  but  when  she  is  opposite 
to  the  Sun,  and  the  Sun  is  never  in  Virgo  or  Libra  except  in 
our  autumnal  months,  September  and  October,  it  is  evident  that 
the  Moon  is  never  full  in  the  opposite  signs,  Pisces  and  Aries, 
except  in  those  two  months.     We  can,  therefore,  have  only  two 
full  Moons  in  a  year,  which  rise,  for  a  week  together,  very  near 
the  time  of  sunset.     The  former  of  these  is  called  the  Harvest 
Moon,  and  the  latter,  the  Hunter's  Moon. 

629.  What  said  of  the  angles  under  which  the  signs  rise  and  set  ?  What  result  follows 
as  to  time  of  the  Moon's  rising  and  setting?  How  illustrate  by  globe  ?  630.  When  is 
the  angle  smallest  in  northern  latitudes?  When  greatest?  What  difference  of  angle  a« 
the  rising  and  setting  of  Pisces?  Daily  difference  of  the  Moon's  rising?  When  in  Piseee 
and  Aries?  What  when  in  Virgo  and  Libra?  631.  Why  have  we  not  more  than  OH* 
Uurvest,  and  one  Hunter's  Moon  in  a  year? 


296  .  AaTRGNOMY. 

632.  Although  there  can  be  but  two  full  Moons  in  the  year 
that  rise  with  r,o  little  variation  of  time,  yet  the  phenomenon 
of  the  Moon's  rising  for  a  week  together  so  nearly  at  the  same 
time,  occurs  every  month,  in  some  part  of  her  course  or  the 
other. 

In  Winter,  the  signs  Pisces  and  Aries  rise  about  noon  ;  hence  the  rising  of  the  Moon 
is  not  then  regarded  nor  perceived. 

In  Spring,  these  signs  rise  with  the  Sun,  because  he  is  then  in  them ;  and  as  the  Moon 
changes  while  passing  through  the  same  sign  with  the  Sun,  it  must  then  be  the  change, 
and  hence  invisible. 

In  Summer,  they  rise  about  midnight,  when  the  Moon,  is  in  her  third  quarter.  On 
account  of  her  rising  so  late,  and  giving  but  little  light,  her  rising  passes  unobserved. 

633.  To  the  inhabitants  at  the  equator,  the  north  and  south 
poles  appear  in  the  horizon,  and  therefore  the  ecliptic  makes  the 
same  angle  southward  with  the  horizon  when  Aries  rises,  as  it 
does  northward  when  Libra  rises  ;  consequently  the  Moon  rises 
and  sets  not  only  with  angles  nearly  equal,  but  at  equal  intervals 
of  time,  all  the  year  round  ;  hence,  there  is  no  harvest  Moon  at 
the  equator.     The  farther  any  place  is  from  the  equator,  if  it  be 
not  bey-ond  the  polar  circles,  the  angle  which  the  ecliptic  makes 
with  the  horizon  gradually  diminishes  when  Pisces  and  Aries  rise. 

634.  Although,  in  northern  latitudes,  the  autumnal  full  Moons 
are  in  Pisces  and  Aries  ;  yet  in  southern  latitudes  it  is  just  the 
reverse,  because  the  seasons  :.re  so  : — for  Yirgo  and  Libra  rise 
at  as  small  angles  with  the  horizon  in  southern  latitudes  as  Pisces 
and  Aries  do  in  the  northern  ;  and  therefore  the  harvest  Moons 
are  just  as  regular  on  one  side  of  the  equator  as  on  the  other. 

At  the  polar  circles,  the  full  Moon  neither  rises  in  summer,  nor  sets  in  winter.  For  the 
winter  full  Moon  being  as  high  in  the  ecliptic  as  the  summer  Sun,  she  must  continue  while 
passing  through  the  northern  signs,  above  the  horizon ;  and  the  summer  full  Moon,  being 
as  low  in  the  ecliptic  as  the  winter  Sun,  can  no  more  rise,  when  passing  through  the 
southern  signs,  than  he  does. 

635.  The  great  apparent  magnitude  of  the  Moon,  and  indeed 
of  the  Sun,  at  rising  and  setting,  is  a  phenomenon  which  has 
greatly  embarrassed  almost  all  who  have  endeavored  to  account 
for  it.     According  to  the  ordinary  laws  of  vision,  they  should 
appear  to  be  least  when  nearest  the  horizon,  being  then  farthest 
from  the  eye  ;  and  yet  the  reverse  of  this  is  found  to  be  true. 
The  apparent  diameter  of  the  Moon,  when  viewed  in  the  horizon 
by  the  naked  eye,  is  two  or  three  times  larger  than  when  at  the 
altitude  of  thirty  or  forty  degrees  ;  and  yet  when  measured  by 
an  instrument  her  diameter  is  not  sensibly  increased. 

682.  Does  not  the  Moon  rise  with  little  variation  for  several  nights  In  succession, 
every  month?  Why  not  always  perceived?  633.  Why  is  there  no  ffarvrt  Moon  at 
the  equator  ?  634.  What  said  of  these  lunar  phenomena  in  the  Southern  .lornisphere  ? 
685.  What  said  of  the  apparent  diameter  of  the  Moon  in  the  horizon?  How  wheu 


REFRACTION    AND    TWILIGHT.  297 

Both  the  Sun  and  the  Moon  really  subtend  a  greater  angle  when  on  the  meridian,  than 
they  do  in  the  horizon  ;  because  they  are  then  actually  nearer  the  place  of  the  spectator 
by  the  whole  semi-diameter  of  the  Earth ;  and  one  reason  why  they  appear  largest  in 
the  horizon  is,  that  they  are  then  compared  with  terrestrial  objects,  with  whose  magni- 
tude we  are  acquainted. 

This  apparent  increase  of  magnitude  in  the  horizontal  Moon,  is  chiefly  an  optical  illu- 
*ion,  produced  by  the  concavity  of  the  heavens  appearing  to  the  eye  to  be  a  less  portion 
of  a  spherical  surface  than  a  hemisphere.  The  eye  is  accustomed  to  estimate  the  dis- 
tance between  any  two  objects  in  the  heavens  by  the  quantity  of  sky  that  appears  to  lie 
between  them ;  as  upon  the  Earth  we  estimate  it  by  the  quantity  of  ground  that  lies 
between  them.  Now  when  the  Sun  or  Moon  is  just  emerging  above  the  eastern  horizon, 
or  sinking  beneath  the  western,  the  cLifttance  of  the  intervening  landscape  over  which 
they  are  seen,  contributes,  together  with  the  refraction  of  the  atmosphere,  to  exaggerate 
our  estimate  of  their  real  magnitudes. 

THE     HORIZONTAL    MOON. 

636.  Both  the  Sun  and  Moon  are  sometimes  seen  to  be  elon, 
gated  horizontally,  when  near  the  horizon.  This  is  often  the  case 
when  the  atmosphere  is  very  dense.  The  cause  of  this  pheno- 
menon is  this  :  All  celestial  bodies  in  the  horizon  are  more  or 
less  elevated  by  atmospherical  refraction  (See  page  300)  ;  and 
the  amount  of  this  apparent  elevation  depends  somewhat  upon 
the  density  of  the  atmosphere  as  well  as  upon  the  altitude  of  the 
object.  When,  therefore,  the  Sun  or  Moon  are  near  the  horizon, 
and  viewed  through  a  dense  atmosphere,  the  refraction  is  great- 
est ;  and  as  their  lower  limb  is  seen  through  a  denser  stratum  of 
atmosphere  than  their  upper  limb,  its  apparent  elevation  is 
greater,  and  the  object  seems  to  be  flattened,  while  its  horizontal 
diameter  is  not  sensibly  diminished. 

This  phenomenon  and  its  cause  may  be  easily  illustrated  by  a  diagram. 


CHAPTER  XYI. 

REFRACTION  AND  TWILIGHT. 

637.  THE  rays  of  light,  in  passing  out  of  one  medium  into 
another  of  a  greater  density,  deviate  from  a  straight  course,  and 
are  bent  towards  a  perpendicular  to  that  course  ;  and  if  the 
density  of  the  latter  medium  continually  increase,  the  rays  of 

measured  ?  When  do  they  subtend  the  greater  angle  ?  Why  appear  largest  when  in 
the  horizon?  What  other  explanation  given?  636.  What  is  meant  by  a  Horiaonttil 
Moon?  The  cause  of  this  phenomenon?  637.  What  is  meant  by  the  refraction  of 
light?  What  principles  govern  it? 


298 


ASTRONOMY. 


LIGHT   REFRACTED   BY   WATER. 

D    G          A 


light  in  passing  through  it,  will  deviate  more  and  more  from  a 
right  line  as  they  pass  downwards,  or  towards  the  eye  of  the 
observer. 

638.  As  air  and  water  are  both  transparent,  but  of  different 
densities,  it  follows  that,  when  light  passes  obliquely  from  one 
to  the  other,  it  will  be 
refracted.  If  it  pass 
from  the  air  into  the 
water,  it  will  be  refract- 
ed towards  a  ptrpendicur 
lar. 

Here  the  ray  A  C  strikes  the 
water  perpendicularly,  and  passes 
directly  through  to  B  without  be- 
ing refracted.  But  the  ray  D  0 
strikes  the  water  at  C  obliquely  ; 
and  instead  of  passing  straight 
through  to  E,  is  refracted  at  C, 
and  reaches  the  bottom  of  the  water  at  P.  If,  therefore,  a  person  were  to  receiye  tha 
ray  into  the  eye  at  F,  and  to  judge  of  the  place  of  the  object  from  which  the  light  ema- 
nates from  the  direction  of  the  ray  C  F,  he  wonld  conclude  that  he  saw  the  object  at  Q-, 
unless  he  made  allowance  for  the  refraction  of  the  light  at  C. 


F 


LIGHT  PROCEEDING   FROM   WATER. 

B 


639.  When  light  passes 
obliquely  from   a  denser 
to   a  rarer    medium,    as 
from  water  into  air,  it  is 
refracted  from  a  perpen- 
dicular towards  a  horizon- 
tal. 

Here  the  lamp  A  shines  up 
through  water  into  air.  The  ray 
that  strikes  the  surface  perpen- 
dicularly passes  on  to  B  without 
oeing  refracted ;  but  the  other  rays 

that  leave  the  water  obliquely  are  refracted  toward  a  horizontal  direction,  In  proportion 
to  their  distance  from  the  perpendicular;  or,  in  other  words,  in  proportion  to  the 
obliquity  of  their  contact  with  the  surface  of  the  water. 

640.  Ill  consequence  of  the  refraction  of  light  towards  a  hori- 
zontal direction,  in  passing  from  water  into  air,  a  pole,  half  of 
which  is  in  the  water,  seems  bent  at  the  surface,  and  the  lower 
end  seems  nearer  the  surface  than  it  really  is.     For  the  same 
reason,  the  bottom  of  a  river  seems  higher,  if  seen  obliquely,  than 
it  really  is  ;  and  the  water  is  always  deeper  than  we  judge  it 
to  be. 


688.  How  refracted  by  air  and  water  ? 
rarer  media?        640.  Effect  of  refraction  upon  objects  seen  un 


639.  How  when  light  passes  from  denser  to 
n  objects  seen  under  water? 


REFRACTION    AND    TWILIGHT. 


299 


In  this  cut,  the  oar,  the  blade  of 
Thich  is  in  the  water,  seems  bent  at  the 
uurface  of  the  water.  The  rays  of  light 
passing  from  the  part  under  water  to 
the  surface  at  D,  are  refracted  toward 
a  horizontal  direction  at  that  point, 
and  received  into  the  eye  of  the  ob- 
server at  B,  who,  judging  of  the  posi- 
tion of  the  immersed  portion  of  the  oar 
from  the  direction  of  the  rays  D  B, 
locates  the  blade  of  the  oar  at  C;  thus 
reversing  the  effect  illustrated  at 


EFFECT   OF   REFRACTION- 


641.  The  refracting  power  of  different  transparent  substances 
depends  mainly  upon  their  density.  Water  refracts  more  than 
air,  glass  more  than  water,  and  diamond  most  of  all.  But  the 
angle  of  incidence,  or  the  obliquity  of  the  contact  of  the  rays 
with  the  denser  substance,  has  also  much  to  do  in  determining 
the  amount  of  refraction. 


EFFECT   OF  REFRACTION 


642.  By  the  aid  of  refraction, 
we  may  see  objects  that  are 
actually  behind  an  opaque  or 
intransparent  body. 

Here  the  piece  of  money  at  A,  at  the 
bottom  of  the  cup,  would  be  invisible  to 
the  behoiuc.  '*  B,  if  the  cup  was  empty, 
as  the  light  from  the  money  would  pass 
from  A  to  C;  but  when  the  oup  is  filled 
with  water,  the  light  is  refracted  to  B,  and 
the  beholder  sees  the  money  apparently 
atD. 


643.  By  the 
law  of  refrac- 
tion, light  has 
been  found  to 
consist  of  a  com- 
bination of  co- 
lors. By  pass- 
ing  a  beam  of 
light  through  a  Blue... 
triangular  piece  YeuJll 

Of       flint      glaSS    grange 

called  a  prism, 
it  is  seen  that 
some  parts  of 


REFRACTION   BY   A   PRISM. 


A 


64!  .  Upon  what  does  the  refracting  power  of  different  transparent  media  depend  ' 
642.  What  other  effect  of  refraction?          643.  What  discovery  by  refraction?      HOT. 


13* 


300 


ASTRONOMY. 


the  light  are  more  refrangible  than  others,  so  that  the  light  is 
analyzed,  or  separated  into  its  component  parts  or  elements. 

Let  a  ray  of  light  from  the  Sun  be  admitted  through  a  hole  in  the  window  shutter,  A, 
into  a  room  from  which  all  other  light  is  excluded  ;  it  will  form  on  a  screen  placed  a  little 
distance  in  front,  a  circular  image,  B,  of  white  light.  Now  iirterpose  near  the  shutter  a 
glass  prism,  C,  and  the  light,  in  passing  through  it,  will  not  only  be  refracted  in  the  same 
direction,  both  when  it  enters  the  prism  and  when  it  leaves  it,  but  the  several  rays  01 
which  white  light  is  composed  will  be  separated,  and  will  arrange  in  regular  order  on  the 
screen,  immediately  above  the  image  B,  which  will  disappear.  The  violet  ray,  it  will  be 
seen,  is  most  refracted,  and  the  red  least ;  the  whole  forming  on  the  scale  an  elongated 
image  of  the  Sun,  called  the  solar  spectrum. — Johnston. 

644.  It  is  the  refraction  of  the  clouds  that  gives  the  sky  its 
beautiful  colors  morning  and  evening  ;  and  the  refracting  power 
of  the  rain-drops  produces  the  beautiful  phenomenon  of  the  rain- 
bow. 


ATMOSPHERICAL    REFRACTION. 

645.  The  refracting  power  of  the  atmosphere  produces  many 
curious  phenomena.     Sometimes  ships  are  seen  bottom  upwards 
in  the  air,  single  or  double.     At  other  times,  objects  really  below 
the  horizon,  as  ships  or  islands,  seem  to  rise  up,  and  to  come  dis- 
tinctly in  view. 

646.  A  very  important  effect  of  refraction,  as  it  relates  to 
astronomy,  is,  that  it  more  or  less  affects  the  apparent  piaces  of 
all  the  heavenly  bodies.     As  the  light  coming  from  them  strikes 
the  atmosphere  obliquely,  and  passes  downward  through  it,  it  is 
refracted  or  bent  towward  the  Earth,  or  toward  a  perpendicular. 
And  as  we  judge  of  the  position  of  the  object  by  the  direction 
of  the  ray  when  it  enters  the  eye,  we  place  objects  higher  in  the 
heavens  than  they  really  are. 

ATMOSPHERICAL   REFRACTION. 

Let  A,  in  the  cut,  repre- 
sent the  Earth ;  B,  the  at- 
mosphere ;  C  C,  the  visible 
horizon  ;  and  the  exterior 
circle  the  apparent  con- 
cave of  the  heavens.  Now, 
as  the  light  passes  from 
the  stars,  and  strikes  the 
atmosphere,  it  is  seen  to 
curve  downward,  because 
it  strikes  the  atmosphere 
obliquely  ;  and  the  air  in- 
sreases  in  density  as  we 
approach  the  Earth.  But 
as  the  amount  of  refraction  depends  not  only  upon  the  density,  but  also  upon  the  obli- 
quity of  the  contact,  it  is  seen  that  the  refraction  is  greatest  at  the  horizon,  and  gradu- 
ally diminishes  till  the  object  reaches  the  zenith,  when  there  is  nc  obliquity,  and  the  refrac- 


344   What  other  effects  of  refraction  ?        645.  Atmospherical  refraction  ?     Efftcu  on 
terrestrial  objeots ':        <.  46.  Upon  apparent  places  of  stars,  Ac.  ? 


REFRACTION    AND    TWILIGHT.  301 

(Ion  whdly  ceases.    The  dark  lines  in  the  cut  show  the  true,  and  the  dotted  the  apparent 
oositions. 

In  the  cut,  the  depth  of  the  atmosphere,  as  compared  with  the  globe,  is  greatly  exag- 
gerated. Even  allowing  it  to  be  50  miles  deep,  it  is  only-J-th  of  the  semi-diameter  of  the 
<?iobe,  which  is  equal  to  only  abouty1^ th  of  an  inch  upon  a  common  13-inch  globe.  But 
.,  was  necesary  to  exaggerate,  in  order  to  illustrate  the  principle. 

647.  The  amount  of  displacement  of  objects  in  the  horizon, 
ty  atmospherical  refraction,  is  about  33',  or  a  little  more  than 
.he  greatest  apparent  diameter  of  either  the  Sun  or  Moon.     It 
/allows,   therefore,   that  when  we  see  the  lower  edge  of  either 
apparently  resting  on  the  horizon,  its  whole  disc  is  in  reality  below 
it ;  and  would  be  entirely  concealed  by  the  convexity  of  the 
Earth,  were  it  not  for  refraction. 

648.  Another  effect  of  refraction  is,  that  the  Sun  seems  to 
rise  about  three  minutes  earlier,  and  to  set  about  three  minutes 
later,  on  account  of  atmospherical  refraction,  than  it  otherwise 
would  ;  thus  adding  about  six  minutes,  on  an  average,  to  the 
length  of  each  day. 

The  atmosphere  is  said  to  be  so  dense  about  the  North  Pole  as  to  bring  the  Sun  above 
the  horizon  some  days  before  he  should  appear,  according  to  calculation.  In  1596,  some 
Dutch  navigators,  who  wintered  at  Nova  Zembla,  in  latitude  76°,  found  that  the  Sun  began 
to  be  visible  17  days  before  it  should  have  appeared  by  calculation  ;  and  Kepler  computes 
that  the  atmospheric  refraction  must  have  amounted  to  5°,  or  10  times  as  much  as  with  us. 

649.  The  twilight  of  morning  and  evening  is  produced  partly 
by  refraction,  but  mainly  by  reflection,     lu  the  morning,  when 
the  Sun  arrives  within  18°  of  the  horizon,  his  rays  pass  over 
our  heads  into  the  higher  region  of  the  atmosphere,  and  are 
thence  reflected  down  to  the  Earth.     The  day  is  then  said  to 
be  dawn,  and  the  light  gradually  increases  till  sunrise.     In  the 
evening,  this  process  is  reversed,  and  the  twilight  lingers  till  the 
Sun  is  18°  below  the  horizon.     There  is  thus  more  than  an  hour 
of  twilight  both  morning  and  evening. 

In  the  arctic  regions,  the  Sun  is  never  more  than  18*  below  the  horizon ;  so  that  the 
twilight  continues  during  the  whole  night. 

650.  In  making  astronomical  observations,  for  the  purposes 
of  navigation,   &c.,  allowance  has  to  be  made  for  refraction, 
according  to  the  altitude  of  the  object,  and  the  state  of  the 
atmosphere.     For  this  pirpose  tables  are  constructed,  showing 
the  amount  of  refraction  :or  every  degree  of  altitude,  from  the 
horizon  to  the  zenith. 

647.  Amount  of  displacement  of  celestial  objects  by  Refraction?  What  follows? 
643.  Influence  of  refraction  on  length  of  days?  How  about  the  North  Pole  ?  649.  Cause 
cfttciliffhtt  650.  What  allowance  ror  refraction  ?  Tables? 


302  ASTRONOMY. 

CHAPTER    XYII. 

AURORA  BOREALIS  AND  PARALLAX. 

651.  THE  sublime  and  beautiful  phenomena  presented  by  the 
Aurora  Borealis,  or  northern  lights,  as  they  are  called,  have  been 
in  all  ages  a  source  of  admiration  and  wonder  alike  to  the  pea- 
sant and  the  philosopher.     In  the  regions  of  the  north  (and 
indeed  in  many  other  places)  they  are  regarded  by  the  ignorant 
with  superstitious  dread,  as  harbingers  of  evil ;  while  all  agree 
in  placing  them  among  the  unexplained  wonders  of  nature. 

These  lights,  or  meteoric  coruscations,  are  more  brilliant  in  the  arctic  regions,  appear- 
ing mostly  in  the  winter  season  and  in  frosty  weather.  They  commonly  appear  at  twi- 
light near  the  horizon,  and  sometimes  continue  in  that  state  for  several  hours  without 
any  sensible  motion ;  after  which  they  send  forth  streams  of  stronger  light,  shooting 
with  great  velocity  up  to  the  zenith,  emulating,  not  unfrequeatly,  the  lightning  in  vivid- 
ness, and  the  rainbow  in  coloring  ;  and  again,  silently  rising  in  a  compact  majestic  arch 
of  steady  white  light,  apparently  durable  and  immovable,  and  yet  so  evanescent,  that 
while  the  beholder  looks  upon  it,  it  is  gone. 

At  other  times  they  cover  the  whole  hemisphere  with  their  flickering  and  fantastic 
coruscations.  On  these  occasions  their  motions  are  amazingly  quick,  and  they  astonish 
the  spectator  with  rapid  changes  of  form.  They  break  out  in  places  where  none  were 
seen  before,  skimming  briskly  along  the  heavens  ;  then  they  are  suddenly  extinguished, 
leaving  behind  an  uniform  dusky  track,  which,  again,  is  brilliantly  illuminated  in  the  same 
manner,  and  as  suddenly  left  a  dull  blank.  Some  nights  they  assume  the  appearance  of 
vast  columns  ;  exhibiting  on  one  side  tints  of  the  deepest  yellow,  and  on  the  other, 
melting  away  until  they  become  undistinguishable  from  the  surrounding  sky.  They 
have  generally  a  strong  tremulous  motion  from  end  to  end,  which  continues  till  the  whole 
vanishes. 

652.  Maupertius  relates,    that   in  Lapland,    "  the   sky  was 
sometimes  tinged  with  so  deep  a  red  that  the  constellation  Orion 
looked  as  though  it  were  dipped  in  blood,  and  that  the  people 
fancied  they  saw  armies  engaged,  fiery  chariots,  and  a  thousand 
prodigies."     Gmelin  relates,  that,  "in  Siberia,  on  the  confines 
of  the  icy  sea,  the  spectral  forms  appear  like  rushing  armies  ; 
and  that  the  hissing,  crackling  noises  of  those  aerial  fireworks 
so  terrify  the  dogs  and  the  hunters,  that  they  fall  prostrate  on 
the  ground,  and  will  not  move  while  the  raging  host  is  passing.' 

Kerguelen  describes  "  the  night  between  Iceland  and  the  Ferro 
Islands,  as  brilliant  as  the  day" — the  heavens  being  on  fire  with 
flames  of  red  and  white  light,  changing  to  columns  and  arches, 
and  at  length  confounded  in  a  brilliant  chaos  of  cones,  pyramids, 
radii,  sheaves,  arrows,  and  globes  of  fire. 

653.  But  the  evidence   of   Captain  Parry  is  of  more  value 

651.  What  said  of  the  Aurora  Borealis t  How  regarded  by  the  ignorant?  Wherr- 
most  brilliant?  In  what  weather?  Describe?  662.  Observations  of  MaurertitA 
Gmtlin,  and  Kerguelen  ?  653.  Observations  of  Capt.  Parry  f 


AClAORA    BOREALIS    AND    PARALLAX.  303 

than  that  of  the  earlier  travelers,  as  he  examined  the  phenomena 
under  the  most  favorable  circumstances,  during  a  period  of 
twenty-seven  consecutive  months,  and  because  his  observations 
are  uninfluenced  by  imagination.  He  speaks  of  the  shifting 
figures,  the  spires  and  pyramids,  the  majestic  arches,  and  the 
sparkling  bands  and  stars  which  appeared  within  the  arctic  cir- 
cle, as  surpassing  his  powers  of  description.  They  are,  indeed, 
sufficient  to  enlist  the  superstitious  feelings  of  any  people  not 
fortified  by  religion  and  philosophy. 

654.  The  colors  of  the  polar  lights  are  of  various  'tints.     The 
rays  or  learns  are  steel  grey,  yellowish  grey,  pea  green,  celandine 
green,  gold  yellow,  violet  blue,  purple,  sometimes  rope  red,  crim- 
son red,  blood  red,  greenish  red,  orange  red,  and  lake  red.    The 
arches  are  sometimes  nearly  black,  passing  into  violet  blue,  grey, 
gold  yellow,  or  white  bounded  by  an  edge  of  yellow.     The  luster 
of  these  lights  varies  in  kind  as  well  as  intensity.     Sometimes  it 
is  pearly,  sometimes  imperfectly  vitreous,  sometimes   metallic. 
Its  degree  of  intensity  varies  from  a  very  faint  radiance  to  a 
light  nearly  equaling  that  of  the  Moon. 

655.  Many  theories  have  been  proposed  to  account  for  this 
wonderful  phenomenon,  but  there  seems  to  be  none  which   is 
entirely  satisfactory.     One  of  the  first  conjectures  on   record 
attributes  it  to  inflammable  vapors  ascending  from  the  Earth 
into  the  polar  atmosphere,  and  there  ignited  by  electricity.     Dr. 
Halley  objects  to  this  hypothesis,  that  the  cause  is  inadequate 
to  produce  the  effect.     He  was  of  opinion  that  the  poles  of  the 
Earth  were  in  some  way  connected  with  the  aurora  ;  that  the 
Earth  was  hollow,  having  within  it  a  magnetic  sphere,  and  that 
the  magnetic  effluvia,  in  passing  from  the  north  to  the  south, 
might  become  visible  in  the  northern  hemisphere. 

656.  That  the  aurora  borealis  is,  to  some  extent,  a  magnetical 
phenomenon,  is  thought,  even  by  others,  to  be  pretty  clearly 
established  by  the  following  considerations  : 

(1.)  It  has  been  observed,  that  when  the  aurora  appears  near 
the  northern  horizon  in  the  form  of  an  arch,  the  middle  of  it  is 
not  in  the  direction  of  the  true  north,  but  in  that  of  the  mag 
netic  needle  at  the  place  of  observation  ;  and  that  when  the 
arch  rises  towards  the  zenith,  it  constantly  crosses  the  heavens 
at  right  angles,  not  to  the  true  magnetic  meridian. 

654.  What  said  of  the  colors,  &c.,  of  these  polar  lights?  655.  Is  there  a  satisfactorj 
explanation  of  these  phenomena?  What  conjecture?  Dr.  Halley's  objection?  His  owr 
singular  opinion  ?  656.  What,  evidences  that  the  Aurora  Jlorealis  is  of  magnetu 
origin  ? 


304  ASTRONOMY. 

(2.)  When  the  beams  of  the  aurora  shoot  up  so  as  to  pass 
whe  zenith,  which  is  sometimes  the  case,  the  point  of  their  con- 
vergence is  in  the  direction  of  the  prolongation  of  the  dipping 
needle  at  the  place  of  observation. 

(3.)  It  has  also  been  observed,  that  during  the  appearance  of 
an  active  and  brilliant  aurora,  the  magnetic  needle  often  becomes 
restless,  varies  sometimes  several  degrees,  and  does  not  resume 
its  former  position  until  after  several  hours. 

From  these  facts,  it  has  been  generally  inferred  that  the  aurora  is  in  some  way  con- 
nected with  the  magnetism  of  the  Earth  ;  and  that  the  simultaneous  appearance  ef  the 
meteor,  and  the  disturbance  of  the  needle,  are  either  related  as  cause  and  effect,  or  as 
the  common  result  of  some  more  general  and  unknown  cause. 

657.  Dr.  Young,  in  his  lectures,  is  very  certain  that  the  phe 
nomenon  in  question  is  intimately  connected  with  electro-mag- 
netism, and  ascribes  the  light  of  the  aurora  to  the  illuminated 
agency  of  electricity  upon  the  magnetical  substance. 

It  may  be  remarked,  in  support  of  the  electro-magnetic  theory,  that  in  magnetism,  the 
agency  of  electricity  is  now  clearly  established,  and  it  can  hardly  be  doubted  that  the 
phenomena  both  of  electricity  and  magnetism  are  produced  by  one  and  the  same  cause  ; 
inasmuch  as  magnetism  may  be  induced  by  electricity,  and  the  electric  spark  has  been 
drawn  from  the  magnet. 

658.  Sir  John  Herschel  also  attributes  the  appearance  of  the 
aurora  to  the  agency  of  electricity.     This  wonderful  agency,  says 
he,  which  we  see  in  intense  activity  in  lightning,  and  in  a  feebler 
and  more  diffused  form  traversing  the  upper  regions  of  the 
atmosphere   in   the   northern   lights,   is   present,   probably,  in 
immense  abundance  in  every  form  of  matter  which  surrounds  us, 
but  becomes  sensible,  only  when  disturbed  by  excitements  of 
peculiar  kinds. 

PARALLAX    OF   THE    HEAVENLY    BODIES. 

659.  Parallax  is  the  difference  between  the  altitude  of  any 
celestial  object  seen  from  the  Earth's  surface,  and  the  altitude 
of  the  same  object  seen  at  the  same  time  from  the  Earth's  cen- 
ter ;  or  it  is  the  angle  under  which  the  semi-diameter  of  the 
Earth  would  appear,  as  seen  from  the  object. 

The  true  place  of  a  celestial  body  is  that  point  of  the  heavens 
in  which  it  would  be  seen  by  an  eye  placed  at  the  center  of  the 
Earth.  The  apparent  place  is  that  point  of  the  heavens  where 
the  body  is  seen  from  the  surface  of  the  Earth.  The  parallax 

657.  Dr.  Young's  opinion?  What  remark  in  support  of  his  views?  653.  Sir  John 
Herschel's  opiniou  ?  659.  Parallax?  True  place  of  a  celestial  body?  Apparent? 
When  parallax  greatest?  Least?  Called  what,  and  why  ?  What  objects  the  greatest 
parallax  ? 


AURORA  BOREAL1S  AND  PARALLAX.         305 

of  a  heavenly  body  is  greatest  when  in  the  horizon,  and  is 
thence  called  the  horizontal  parallax.  Parallax  decreases  as  the 
body  ascends  towards  the  zenith,  at  which  place  it  is  nothing. 

The  adjoining  cut  will  afford  a  sufficient  illustration. 

When  the  observer,  standing  upon  the  Earth  at  A,  PARALLAX  OF  THE  PLANKTS. 
views  the  object  at  B,  it  appears  to  be  at  C,  when,  at 
the  same  time,  if  viewed  from  the  center  of  the  Earth, 
it  would  appear  to  be  at  D.  The  parallax  is  the  angle 
B  C  D  or  A  B  E,  which  is  the  difference  between  the 
altitude  of  the  object  B,  when  seen  from  the  Earth's 
surface,  and  when  seen  from  her  center.  It  is  also 
the  angle  under  which  the  semi-diameter  of  the  Earth, 
A  E,  is  seen  from  the  object  B. 

As  the  object  advances  from  the  horizon  to  the 
zenith,  the  parallax  is  seen  gradually  to  diminish,  till 
at  F  it  has  no  parallax,  or  its  apparent  and  true  place 
are  the  same. 

This  diagram  will  also  show  why  objects  nearest 
the  Earth  have  the  greatest  parallax,  and  those  most 
distant  the  least;  why  the  Moon,  the  nearest  of  all 
the  heavenly  bodies,  has  the  greatest  parallax  ;  while 
the  fixed  stars,  from  their  immense  distance,  have  no 
appreciable  horizontal  parallax — the  semi-diameter 
of  the  Earth,  at  such  a  distance,  being  no  more  than  a  point. 

660.  As  the  effect  of  parallax  on  a  heavenly  body  is  to  depress 
it  below  its  true  place,  it  must  necessarily  affect  its  right  ascen- 
sion and  declination,  its  latitude  and  longitude.     On  this  account, 
the  parallax  of  the  Sun  and  Moon  must  be  added  to  their 
apparent  altitude,  in  order  to  obtain  their  true  altitude. 

The  true  altitude  of  the  Sun  and  Moon,  except  when  in  the  zenith,  is  always  affected, 
more  or  less,  both  by  parallax  and  refraction,  but  always  in  a  contrary  manner.  Hence 
the  mariner,  in  finding  the  latitude  at  sea,  always  adds  the  parallax,  and  subtracts  the 
refraction,  to  and  from  the  Sun's  observed  altitude,  in  order  to  obtain  the  true  altitude, 
and  thence  the  latitude. 

661.  The  principles  of  parallax  are  of  great  importance  to 
astronomy,  as  they  enable  us  to  determine  the  distances  of  the 
heavenly  bodies  from  the  Earth,  the  magnitudes  of  the  planets 
and  the  dimensions  of  their  orbits. 

The  Sun's  horizontal  parallax  being  accurately  known,  the 
Earth's  distance  from  the  Sun  becomes  known  ;  and  the  Earth's 
distance  from  the  Sun  being  known,  that  of  all  the  planets  may 
be  known  also,  because  we  know  the  exact  periods  of  their 
sidereal  revolutions,  and,  according  to  the  third  law  of  Kepler, 
the  squares  of  the  times  of  their  revolutions  are  proportional  to 
the  cubes  of  their  mean  distances.  Hence,  the  first  great 
desideratum  in  astronomy,  where  measure  and  magnitude  are 
concerned,  is  the  determination  of  the  true  parallax. 

At  a  council  of  astronomers  assembled  in  London  some  years  since,  from  the  m<vt 

660.  Effect  of  parallax  ?  How  obtain  true  altitude  ?  How  differ  from  refraction  F 
Dow  then  obtain  true  altitude  ?  661.  Use  of  parallax  ?  How  employed  ?  Note  ? 


306 


ASTRONOMY. 


learned  nations  in  Enrope,  the  Sun's  mean  horizontal  parallax  was  settled,  as  the  n-*.i? 
of  their  united  observations,  at  0*  0'  8".6776.  Now  the  value  of  radius,  expressed  like- 
wise in  seconds,  is  206264"  .8;  and  this  divided  by  8".5776,  gives  24047  for  the  distance  of 
the  Sun  from  the  the  Earth,  in  semi-diameters  of  the  latter.  If  we  take  the  equatorial 
semi-diameter  of  the  Earth,  as  sanctioned  by  the  same  tribunal,  at  (7924+2=)  3962  tiiles, 
we  shall  have  24047  x  3962= 95,273,869  miles  for  the  Sun's  true  distance. 

A  TABLE  OK  THE  SUN'S  PARALLAX  IN  ALTITUDE. 


Sun's 

Aim. 

Sun's  Horizontal  Parallax. 

Sun's 
Altit. 

Sun's  Horizontal  Parallax. 

8.4 

8.5 

8.6 

8.7 

8.8 

8.4 

8.5 

8.6 

8.7 

8.8 

0 

8.40 

8.50 

8.60 

8.70 

8.80 

45 

5.94 

6.01 

6.08 

6.15 

6.22 

5 

8.87 

8.47 

8.57 

8.67 

8.77 

50 

5.40 

5.46 

5.53 

5.59 

5.66 

10 

8.27 

8.37 

8.47 

8.57 

8.67 

55 

4.82 

4.88 

4.93 

4.99 

5.05 

15 

8.11 

8.21 

8.31 

8.40 

8.50 

60 

4.20 

4.25 

4.30 

4.35 

4.40 

20 

7.89 

7.99 

8.08 

8.18 

8.27 

65 

8.55 

8.59 

3.63 

8.68 

3.72 

25 

7.61 

7.70 

7.79 

7.88 

7.98 

70 

2.87 

2.91 

2.94 

2.98 

3.01 

30 

7.28 

7.36 

7.45 

7.53 

7.62 

75 

2.17 

2.20 

2.23 

2.25 

2.28 

35 

6.88 

6.96 

7.04 

7.13 

7.21 

80 

1.46 

1.48 

1.49 

1.51 

1.53 

40 

6.44 

6.51 

6.59 

6.66 

6.74 

85 

0.73 

0.74 

0.75 

0.76 

0.77 

45 

5.94 

6.01 

6.08 

6.15 

6.22 

90 

0.00 

0.00 

0.00 

0.00 

0.00 

662.  The  change  in  the  apparent  position  of  the  fixed  stars, 
caused  by  the  change  of  the  Earth's  place  in  her  revolution 
around  the  Sun,  is  called  their  annual  parallax.  So  immense 
is  their  distance,  that  the  semi-annual  variation  of  190,000,000 
of  miles  in  the  Earth's  distance,  from  all  those  stars  that  lie  in 
the  plane  of  her  orbit,  makes  no  perceptible  difference  in  their 
apparent  magnitude  or  brightness. 

The  following  cut  will  illustrate  our  meaning: 


B 

Let  A  represent  a  fixed  star  in  the  plane  of  the  Earth's  orbit,  B.  At  C,  the  Earth  is 
190,000,000  of  miles  nearer  the  star  than  it  will  be  at  D  six  months  afterward  ;  and  yet 
this  serai-annual  variation  of  190,000,000  miles  in  the  distance  of  the  star  is  so  small  a 
fraction  of  the  whole  distance  to  it,  as  neither  to  increase  or  diminish  its  apparent 
brightness. 

663.  It  is  only  those  stars  that  are  situated  near  the  axis  of 
the  Earth's  orbit  whose  parallax  can  be  measured  at  all,  on 


662.  What  meant  by  Earth's  annual  parallax  f    Effect  of  variation  of  Earth's  d!s- 
on  the  fixed  stars?     Diagram.        663.  What  stars  have  perceptible  parallax 'i 


AURORA    BOREALIS    AND    PARALT^X.  307 

account  of  its  almost  imperceptible  quantity. 
So  distant  are  they,  that  the  variation  of 
190,000,000  miles  in  the  Earth's  place 
causes  an  apparent  change  of  less  than  1'  in 
the  nearest  and  most  favorably  situated 
fixed  star. 

Let  A  represent  the  Earth  on  the  1st  of  January,  and  B  a 
star  observed  at  that  time.  Of  course,  its  apparent  place  in 
the  more  distant  heavens  will  be  at  C.  But  in  six  months  the 
Earth  will  be  at  D,  and  the  star  B  will  appear  to  be  at  E. 
The  angle  A  B  D  or  0  B  E  will  constitute  the  parallactic  angle. 
In  the  cut,  this  angle  amounts  to  about  48°,  whereas  the  real 
parallax  of  the  stars  is  less  than  — 1-th  of  one  degree,  or 
"^  IMF  o"tn  Part  °^  tnis  amounk  Lines  approaching  each  other 
thus  slowly  would  appear  parallel ;  and  the  Earth's  crbit,  if 
filled  with  a  globe  of  fire,  and  viewed  from  the  fixed  stars, 
would  appear  but  a  point  of  light  1'  in  diameter  !  For  a 
splendid  diagram  illustrative  of  the  annual  parallax  of  the  stars,  see  Map  I.,  of  the  Atlas. 

ABERRATION   OF   LIGHT. 

664.  In  the  year  1725,  Mr.  Molyneux  and  Dr.  Bradley  fixed 
up  a  very  accurate  and  costly  instrument,  in  order  to  discover 
whether  the  fixed  stars  had  any  sensible  parallax,  while  the  Earth 
moved  from  one  extremity  of  its  orbit  to  the  other ;  or  which 
is  the  same,  to  determine  whether  the  nearest  fixed  stars  are 
situated  at  such  an  immense  distance  from  the  Earth,  that  any 
star  which  is  seen  this   night,  directly  north  of  us,  will,  six 
months  hence,  when  we  shall  have  gone  190,000,000  of  miles  to 
the  eastward  of  the  place  we  are  now  in,  be  then  seen  exactly 
north  of  us  still,  without  changing  its  position  so  much  as  the 
thickness  of  a  spider's  web. 

665.  These  observations  were  subsequently  repeated,  with  but 
little  intermission,  for  twenty  years,  by  the  most  acute  observers 
in  Europe,  and  with  telescopes  varying  from  12  feet  to  36  feet 
in  length.     In  the  mean  time,  Dr.  Bradley  had  the  honor  of 
announcing   to   the  world  the  very  nice  discovery  made  while 
endeavoring  to  ascertain  the  parallax  of  the  fixed  stars,  that 
the   motion  of  light,  combined  with,  tJie  progressive  motion  of  the 
Earth  in  its  orbit,  causes  the  heavenly  bodies  to  be  seen  in  a  differ- 
ent position  from  what  they  would  be,  if  the  eye  were  at  rest.     Thus 
was  established  the  principle  of  the  Aberration  of  Light. 

666.  This  principle,  or  law,  now  that  it  is  ascertained,  seems 

Amount?  Diagram,  and  explanation.  664.  What  experiment  by  Molyneux  ana 
Bradley?  With  what  results?  665.  What  further  observations  for  the  same  purpose.  V 
What  discovery  made  while  investigating  the  subject  of  parallax  ?  What  is  the  aberrn- 
tlon  of  light  ?  666  What  remarks  upon  the  principle  or  law  of  observation  ?  He  w  ia 


308  ASTRONOMY. 

not  only  very  plain,  but  self-evident.  For  if  light  be  progres- 
sive, the  position  of  the  telescope,  in  order  to  receive  the  ray, 
must  be  different  from  what  it  would  have  been  if  light  had 
been  instantaneous,  or  if  the  Earth  stood  still.  Hence  the  place 
to  which  the  telescope  is  directed  will  be  different  from  the  \rue 
place  of  the  object. 

The  quantity  of  this  aberration  is  determined  by  a  simple 
proposition.  The  Earth  describes  59'  8"  of  her  orbit  in  a  day 
=  3548",  and  a  ray  of  light  comes  from  the  Sun  to  us  in  8'  13" 
=493":  now  24  hours  or  86400"  :  493:  :3548:  22";  which 
is  the  change  in  the  star's  place,  arising  from  the  cause  above- 
mentioned. 


CHAPTER  XYIII. 

PRACTICAL    ASTRONOMY— REFLECTION    AND    REFRAC- 
TION OF  LIGHT. 

667.  Practical  Astronomy  has  respect  to  the  means  employed 
for  the  acquisition  of  astronomical  knowledge.     It  includes  the 
properties  of  light,  the  structure  and  use  of  instruments,  and 
the  processes  of  mathematical  calculation. 

In  the  present  treatise,  nothing  further  will  be  attempted  than  a  mere  introduction  tc 
practical  astronomy.  In  a  work  designed  for  popular  use,  mathematical  demonstrations 
would  be  out  of  place.  Still,  e  very  student  in  astronomy  should  know  how  telescopes  are 
made,  upon  what  laws  they  depend  for  their  power,  and  how  they  are  used.  It  is  for  thid 
purpose  mainly  that  we  add  the  following  chapters  on  practical  astronomy. 

PROPERTIES    OF   LIGHT. 

668.  Light  is  that  invisible  ethereal  substance  by  which  we 
are   apprised  of  the  existence,  forms,  and  colors  of  material 
objects,  through  the  medium  of  the  visual  organs.     To  this  sub- 
tile fluid  we  are  especially  indebted  for  our  knowledge  of  those 
distant  worlds  that  are  the  principal  subjects  of  astronomical 
inquiry. 

669.  The  term  light  is  used  in  two  different  senses.     It  may 
signify  either  light  itself,  or  the  degree   of  light  by  which  we  are 
enabled  to  see  objects  distinctly.     In  this  last  sense,  we  put  light 

the  quantity  of  aberration  determined  ?  667.  Subject  of  Chapter  XVIII.  ?  What  is 
practical  astronomy  t  How  far  discussed  in  this  treatise?  668.  Define  light.  For 
what  indebted  to  it?  669.  Different  senses  in  which  the  term  is  used?  What  b 


REFLECTION    AND    REFRACTION    OF    LIGHT.  30l> 

in  opposition  to  darkness.  But  it  should  be  borne  in  mind,  that 
darkness  is  merely  the  absence  of  that  degree  of  light  which  is 
necessary  to  human  vision  ;  and  when  it  is  dark  to  us,  it  may  be 
light  to  many  of  the  lower  animals.  Indeed,  there  is  more  or 
less  light,  even  in  the  darkest  night,  and  in  the  deepest  dungeon. 

"  Those  unfortunate  individuals,"  says  Dr.  Dick,  "  who  have  been  confined  in  the  dark- 
est dungeons,  have  declared,  that  though,  on  their  first  entrance,  no  object  could  be  per- 
ceived, perhaps  for  a  day  or  two,  yet,  in  the  course  of  time,  as  the  pupils  of  their  eyes 
expanued,  they  could  readily  perceive  rats,  mice,  and  other  animals  that  infested  their 
cells,  and  likewise  the  walls  of  their  apartments ;  which  shows  that,  even  in  such  situa- 
tions, light  is  present,  and  produces  a  certain  degree  of  influence." 

670.  Of  the  nature  of  the  substance  we  call  light,  two  theo 
ries  have  been  advanced.     The  first  is,  that  the  whole  sphere  of 
the  universe  is  filled  with  a  subtile  fluid,  which  receives  from 
luminous  bodies  an  agitation  ;  so  that,  by  its  continued  vibra- 
tory motion,  we  are  enabled  to  perceive  luminous  bodies.     This 
was  the  opinion  of  Descartes,  Euler,  Huygens,  and  Franklin. 

The  second  theory  is,  that  light  consists  of  particles  thrown 
off  from  luminous  bodies,  and  actually  proceeding  through  space. 
This  is  the  doctrine  of  Newton,  and  of  the  British  philosophers 
generally. 

Without  attempting  to  decide,  in  this  place,  upon  the  relative  merits  of  these  two  hypo- 
theses, we  shall  use  those  terms,  for  convenience  sake,  that  indicate  the  actual  passage 
of  light  from  one  body  to  another. 

671.  Light  proceeds  from  luminous  bodies  in  straight  lines, 
and  in  all  directions.     It  will  not  wind  its  way  through  a  crooked 
passage,  like  sound  ;  neither  is  it  confined  to  a  part  of  the  cir- 
cumference around  it. 

As  the  Sun  may  be  seen  from  every  point  in  the  solar  system,  and  far  hence  into  space 
'n  every  direction,  even  till  he  appears  but  a  faint  and  glimmering  star,  it  is  evident  that 
he  fills  every  part  of  this  vast  space  with  his  beams.  And  the  same  might  be  said  of 
every  star  in  the  firmament. 

672.  As  vision  depends  not  upon  the  existence  of  light  merely, 
but  requires  a  certain  degree  of  light  to  emanate  from  the  object, 
and  to  enter  the  pupil  of  the  eye,  it  is  obvious  that  if  we  can, 
by  any  means,  concentrate  the  light,  so  that  more  may  enter  the 
eye,  it  will  improve  our  perception  of  visible  objects,  and  even 
enable  us  to  see  objects  otherwise  wholly  invisible. 

Some  animals  have  the  power  of  adapting  their  eyes  to  the  existing  degree  of  lighC 
The  cat,  horse,  &c.,  can  see  day  or  night;  while  the  owl,  that  sees  well  in  the  night,  sees 
poorly  in  the  day-time. 

673.  Light  may  be  turned  out  of  its  course  either  by  reflection 

darkless  ?  Can  it  be  dark  and  light  at  the  same  time  ?  Is  there  any  place  without 
light?  Quotation  from  Dr.  Dick?  670.  What  theories  of  the  nature  of  light,  and  by 
Whom  supported  respectively?  Remark  of  author?  671.  How  light  proceeds  from 
'uminous  bodies  ?  Radiations  from  Sun  and  stars  ?  672.  How  improve  vision,  and 
Vhy  ?  Animals  ?  673.  How  is  light  turned  out  of  its  course  ? 


310 


ASTRONOMY. 


or  refraction.  It  is  reflected  when  it  falls  upon  the  highly  polished 
surface  of  metals  and  other  intranspareiit  substances  ;  and 
refracted  when  it  passes  through  transparent  substances  of  diffe- 
rent densities,  as  already  illustrated  in  Chapter  XYI. 


REFRACTION  BY  GLASS   LENSES. 


674.  A  lens  is  a  piece  of  glass,  or  other  transparent  substance, 
of  such  a  form  as  to  collect  or  disperse  the  rays  of  light  that 
are  passed  through  it,  by  refracting  them  out  of  a  direct  course. 
They  are  of  different  forms,  and  have  different  powers. 


In  the  adjoining  cut,  we  have  an  edgewise 
view  of  six  different  lenses. 

A  is  the  plano-convex,  or  half  a  double  con- 
vex lens ;  one  side  being  convex  and  the  other 
plane. 

B  is  a  plano-concave  ;  one  surface  being  con- 
cave, and  the  other  plane. 

C  is  a  double-convex  lens,  or  one  that  is 
bounded  by  two  convex  surfaces. 

I)  is  a  double-concave  lens,  or  a  circular  piece 
of  glass  hollowed  out  on  both  sides. 

E  is  a  concavo-convex  lens,  whose  curves 
differ,  but  do  not  meet,  if  produced. 

P  is  a  meniscus,  or  a  concavo-convex  lens, 
the  curves  of  whose  surfaces  meet. 


LENSES  OF  DIFFERENT  FORKS. 


675.  A  double-convex  lens 
converges  parallel  rays  to  a 
point  called  the  focus ;  and 
the   distance    of   the   focus 
depends  upon  the  degree  of 
cocvexity. 

In  the  first  of  these  cuts,  the  lens  is 
quite  thick,  and  the  focus  of  the  rays  is 
quite  near ;  but  the  other  being  less 
convex,  the  focus  is  more  distant. 

676.  The   distance   of  the 
focus  of  a  double-convex  glass 
lens  is  the  radius  of  the  sphere 
of  its  convexity. 

In  this  cut,  it  will  be  seen  that  the 
parallel  rays  A  are  refracted  to  a  focus 
at  C,  by  the  double-convex  lens  B,  the 
convexity  of  whose  surfaces  is  just  equal 
to  the  curve  of  the  circle  D. 

677.  The  focal  distance  of 
a  plano-convex  lens  is  equal  to 
the  diameter   of   the   sphere 

formed  by  the  convex  surface  produced. 


LIGHT     REFRACTED  BY   LENSES. 


DOUBLE    CONVEX — FOCAL    DISTANCE. 


6T4.  What  is  a  lens  ?  Draw  and  describe  different  kinds.  675.  Refracting  power  of 
double-convex  lens?  Focal  distance?  Diagram,  and  illustrate.  6T6.  Hew  focal  dis- 
tance governed  ?  Diagram,  and  illustrate.  677.  What  is  the  focal  distance  of  a 


REFLECTION    AND    REFRACTION    OF    LIGHT. 


311 


It  must  be  borne  in  mind,  that  PLANO-CONCAVB— FOCAL  DISTANCT. 

light  is  refracted  both  when  it 
enters,  and  when  it  lea  res  a  double 
convex  lens,  and  in  both  instances 
in  the  same  direction  ;  and,  so  far 
as  the  distance  of  the  focus  is 
concerned,  to  the  same  extent. 
But  when  the  lens  is  convex  only 
on  one  side,  half  its  refracting 
power  is  gone,  so  that  the  rays 
are  not  so  soon  refracted  to  a 
focus.  In  this  case,  the  focal  dis- 
tance is  equal  to  the  diameter  of 
the  sphere  formed  by  extending 
the  convex  surface  of  the  lens; 
while  with  the  double-convex  lens, 
the  focal  distance  is  only  equal  to 
the  radius  of  such  sphere.  In  the  cut,  the  parallel  rays  A  ure  refracted  to  a  focus  at 
B,  by  the  plano-concave  lens  C ;  and  the  distance  C  B  is  the  diameter  of  the  circle 
D,  formed  by  the  convex  surface  of  the  lens  C  produced. 

678.  A    double-cm- 
cave  lens  disperses  pa- 
rallel rays,  as  if  they 
diverged  from  the  cen- 
ter of  a  circle  formed 
by  the  convex  surface 
produced. 

In  this  cut,  the  parallel  rays 
A  are  dispersed  by  the  double- 
concave  lens  C,  as  shown  at 
B;  and  their  direction,  as 
thus  refracted,  is  the  same 
as  if  they  proceeded  from  the  point  D,  which  is  the  center  of  a  circle  formed  by  the 
concave  surface  of  the  lens  produced. 

679.  Common  spectacles,  opera-glasses,  burning-glasses,  and 
refracting  telescopes  are  made  by  converging  light  to  a  focus,  by 
the  use  of  double-convex  lenses. 


RAYS   DISPERSED   BV   REFRACTION. 


\ 


BCRNINQ-GLASS. 


The  ordinary  burning-glass,  which  may  be 
bought  for  a  few  shillings,  is  a  double-convex 
disk  of  glass  two  or  three  inches  in  diameter, 
inclosed  in  a  slight  metallic  frame,  with  a  han- 
dle on  one  side.  Old  tobacco-smokers  some- 
times carry  them  in  their  pockets,  to  light  their 
pipes  with  when  the  Sun  shines.  In  other  in- 
stances, they  have  been  so  placed,  as  to  fire  a 
cannon  in  clear  weather,  by  igniting  the  prim- 
ing at  12  o'clock. 

The  adjoining  cut  represents  a  large  burn- 
ing-glass converging  the  rays  of  the  Sun  to  a 
focus,  and  setting  combustible  substances  on 
fire.  Such  glasses  have  been  made  powerful 
enough  to  melt  the  most  refractory  substances, 
as  platinum,  agate,  &c.  "  A  lens  three  feet  in 
diameter,"  says  Professor  Gray,  "  has  been 
known  to  melt  cornelian  in  75  seconds,  and  a 
piece  of  white  agate  in  30  seconds." 


plano-convex  lens ?  Diagram.  6T8.  Effect  of  double-conv&c  lens?  Amount  of  diver 
poncy  of  rays?  679.  What  articles  made  with  double-convex  lenses  ?  Uses?  Powe» 
of  burning  glasses? 


312 


ASTRONOMY 


REFLECTION   OF  LIGHT. 

680.  We  have  now  shown  how  light  may  be  turned  out  of  its 
courso,  and  analyzed,  dispersed,  or  converged  to  a  point  by 
refraction.  Let  us  now  consider  how  it  may  be  converged  to  a 
focus  by  reflection. 

When  light  falls  upon  a  highly-polished  surface,  especially  of 
metals,  it  is  reflected  or  thrown  off  in 
a  new  direction,  and  the  angles  of 
contact   and  departure   are   always 
equal. 

Let  A  B  represent  the  -polished  metallic  surface, 
C  the  source  of  light,  and  the  arrows  the  direction 
of  the  ray.  Then  D  would  represent  the  angle  of 
incidence  or  contact,  and  E  the  angle  of  reflection 
or  departure — which  angles  are  seen  to  be  equal.  A. 


REFEECTION   BY   A  PLANJQ  1IIUK011. 


REFLECTION   BY  A  CONCAVE  MIRROR. 


681.  A  concave  mirror  re- 
flects parallel  rays  back  to  a 
focus,  the  distance  of  which 
is  equal  to  half  the  radius  of 
the   sphere  formed  by  the 
concave  surface  produced. 

In  this  cut,  the  parallel  rays  A  fail 
upon  the  concave  mirror  B  B,  and  are 
reflected  to  the  focus  C,  which  is  half 
the  radius  of  the  sphere  formed  by  the 
surface  of  the  mirror  produced.  If, 
therefore,  it  was  desirable  to  construct 
a  concave  mirror,  having  its  focus  10 
feet  distant,  it  would  only  be  necessary 
to  grind  it  on  the  circle  of  a  sphere 
having  a  radius  of  20  feet. 

682.  In  reflection,  a  por- 
tion of  the  light  is  absorbed 
or  otherwise  lost,  so  that  a 
reflector  of  a  given  diameter 

will  not  converge  as  much  light  to  a  focus  as  a  double-convex 
lens  of  the  same  size.  In  the  latter  case  all  the  light  is  trans- 
mitted. Still,  reflectors  have  been  found  of  such  power  as  to 
melt  iron,  and  other  more  difficult  substances. 

We  have  now  considered  so  much  of  optics  as  is  necessary  to  an  understanding  of  the 
principles  upon  which  telescopes  are  constructed;  and,  for  further  particulars,  shaU 
refer  the  student  to  books  on  Natural  Philosophy. 


6SO.  What  now  shown  in  this  chapter?  What  next?  What  is  reflect  ion,  and  when 
1oes  it  take  place?  What  law  governs  it?  Diagram.  681.  How  does  a  concave: 
mirror  reflect  parallel  rays  1  Distance  of  focus  ?  Diagram.  How  would  you  construct 
a  concave  mirror  with  a  10  feet  focus  ?  6S2.  Is  all  the  light  falling  upon  a  polished 
surface  reflected  ?  What  then  ?  Closing  note  ? 


TELESCOPES REFKACTORS    AND   REFLECTORS.         318 

/      '.       /    '".  *•       .,.,•.:.,,,-.-_•  , 

CHAPTER  XIX. 
TELESCOPES— KEFKACTORS  AND  REFLECTORS. 

683.  A  TELESCOPE  is  an  optical  instrument  employed  in  view- 
ing distant  objects,  especially  the  heavenly  bodies.     The  term 
telescope  is  derived  from  two  Greek  words,  viz.,  tele,  at  a  distance, 
and  tkopeo,  to  see.     So  far  as  is  now  known,  the  ancients  had  no 
knowledge  of  the  telescope.     Its  invention,  which  occurred  in 
1609,  is  usually  attributed  to  Galileo,  a  philosopher  of  Florence, 
in  Italy. 

The  discovery  of  the  principle  upon  which  the  refracting  telescope  is  constructed  waa 
purely  accidental.  The  children  of  one  Jnnfsen,  a  spectacle-maker  of  Middleburgh,  in 
Holland,  being  at  play  in  their  father's  shop,  happened  to  place  two  glasses  in  such  a 
manner,  that  in  looking  through  them,  at  the  weathercock  of  the  church,  it  appeared  to 
be  nearer,  and  much  larger  than  usual.  This  led  their  father  to  fix  the  glasses  upon  a 
board,  that  they  might  be  ready  for  observation ;  and  the  news  of  the  discovery  was  soon 
conveyed  to  the  learned  throughout  Europe.  Galileo  hearing  of  the  phenomenon,  sooc 
discovered  the  secret,  and  put  the  glasses  in  a  tube,  instead  of  on  a  board ;  and  thus  the 
first  telescope  was  constructed. 

684.  The  telescope  of  Galileo  was  but  one  inch  in  diameter, 
and  magnified  objects   but   30   times.     Yet  with    this   simple 
instrument  he  discovered  the  face  of  the  Moon  to  be  full  of  ine- 
qualities, like  mountains  and  valleys  ;  the  spots  on  the  Sun  ;  tho 
phases  of  Yenus  ;  the  satellites  of  Jupiter  ;  and  thousands  of 
new  stars  in  all  parts  of  the  heavens. 

Notwithstanding  this  propitious  commencement,  so  slow  was  the  progress  of  the 
telescope  towards  its  present  state,  that  in  1816,  Bonnycastle  speaks  of  the  30- fold  mag- 
nifying power  of  the  telescope  of  Galileo  as  "  nearly  the  greatest  perfection  that  thia 
Kind  of  telescope  is  capable  of  1" 

685.  If  he  be  the  real  author  of  an  invention  who,  from  a 
knowledge  of  the  cause  upon  which  it  depends,  deduces  it  from 
one  principle  to  another,  till  he  arrives  at  the  end  proposed, 
then  the  whole  merit  of  the  invention  of  the  telescope  belongs  to 
Galileo.     The  telescope  of  Jansen  was  a  rude  instrument  of  mere 
curiosity,  accidentally  arranged  ;  but  Galileo  was  the  first  who 
constructed  it  upon  principles  of  science,  and  showed  the  practi- 
cal uses  to  which  it  might  be  applied. 

It  is  said  that  the  original  telescope  constructed  by  Galileo  is  still  preserved  in  the 
British  Museum.  A  pigmy,  indeed,  in  its  way,  but  the  honored  progenitor  of  a  race  of 
giants ! 

686.  The  discovery  of  the  telescope  tended  greatly  to  sustain 

683.  Subject  of  Chapter  XIX.  ?  Telescope  ?  Derivation  ?  Ancient  or  modern  ?  In- 
ventor? Incidents  of  discovery?  684.  Galileo's  telescope?  Discoveries  with  it? 
Progress  Sn  telescope  making?  686.  Is  Galileo  entitled  to  the  honor  of  inventing  the 
tclcoco^e ?  Where  is  his?  686.  Relation  of  discovery  to  Coperuican  theory?  Meets 


3  it  ASTRONOMY. 

the  Copernican  theory,  which  had  just  been  promulgated,  and  of 
which  Galileo  was  an  ardent  disciple.  Like  Copernicus,  how 
ever,  his  doctrines  subjected  him  to  severe  persecutions,  and  he 
was  obliged  to  renounce  them. 

The  following  is  his  renunciation,  made  June  28,1638:  "  I,  Galileo,  in  the  seventieth 
year  of  my  age,  on  bended  knees  before  your  eminences,  having  before  my  eyes  and 
touching  with  my  hands  the  Holy  Gospels,  I  curse  and  detest  the  error  of  the  Earth's 
movement."  As  he  left  the  court,  however,  after  this  forced  renunciation,  he  is  said  to 
have  stamped  upon  the  Earth,  and  exclaimed,  "  It  does  move,  after  all?"  Ten  years 
after  this,  he  was  sent  to  prison  for  the  same  supposed  error ;  and  soon,  his  age  advanc- 
ing, the  grave  received  him  from  the  malice  of  his  persecutors. 

DIFFERENT   KINDS    OF   TELESCOPES. 

687.  Telescopes  are  of  two  kinds — Reflectors  and  Refractors. 
Refracting  telescopes  are  made  by  refracting  the  light  to  a  focus 
with  a  glass  lens  (675)  ;  and  reflecting  telescopes,  by  reflecting 
it   to   a  focus   with   a  concave   mirror    (681).     Besides   this 
general  division,  there  are  various  kinds  both  of  reflectors  and 
refractors. 

Telescopes  assist  -vision  in  various  ways— first,  by  enlarging  the  visual  angle  under 
which  a  distant  object  is  seen,  and  thus  magnifying  that  object ;  and,  secondly,  by 
converging  to  a  point  more  light  than  could  otherwise  enter  the  eye— thus  rendering 
objects  distinct  or  visible  that  would  otherwise  be  indistinct  or  invisible. 

All  the  light  falling  upon  a  six  or  a  twelve  inch  lens  may  be  converged  to  a  focus,  so 
as  to  be  taken  into  the  human  eye  through  the  pupil,  which  is  but  one-fourth  of  an  inch 
in  diameter.  Our  vision  is  thus  made  as  perfect  bj  art  as  if  nature  had  given  us  ability 
to  enlarge  the  eye  till  the  pupil  was  a  foot  in  diameter. 

688.  Refracting  telescopes  may  consist  of  a  double-convex 
lens  placed  upon  a  stand,  without  tube  or  eye-piece.     Indeed,  a 
pair  of  ordinary  spectacles  is  nothing  less  than  a  pair  of  small 
telescopes,  for  aiding  impaired  vision. 

REFRACTING  TELESCOPE  WITH  A  SINGLE  LENS. 


Here  the  parallel  rays  are  seen  to  pass  through  the  lens  at  A,  and  to  be  so  converged 
to  a  point  as  to  enter  the  eye  of  the  beholder  at  B.  His  eye  is  thus  virtually  enlarged  to 
the  size  of  the  lens  at  A.  But  it  would  be  very  difficult  to  direct  such  a  telescope  toward 
celestial  objects,  or  to  get  the  eye  5n  the  focus  after  it  was  thus  directed. 


upon   Galileo?      His  renunciation?      Death?        687.  Kinds  of  telescopes?    Dcccrib-i. 
Uow  assist  vision?    Illustration.        688.  Simplest  form  of  refracting  telescope  V 


TELESCOPES REFRACTORS    AND    REFLECTORS.         315 

689.  The  Galilean  telescope  consists  of  two  glasses — a  double- 
convex  next  the  object,  and  a  double-concave  near  the  eye.  The 
former  converges  the  light  till  it  can  be  received  by  a  small 
double-concave,  by  which  the  convergency  is  corrected  (502), 
and  the  rays  rendered  parallel  again,  though  in  so  small  a  beam 
as  to  be  capable  of  entering  the  eye. 

GALILEAN  THLE800PB. 


Here  the  light  is  converged  by  the  lens  A,  till  it  can  be  received  by  the  double-concave 
lens  B,  by  which  the  rays  are  made  to  become  a  small  parallel  beam  that  can  enter  the 
eye  at  C.  This  was  the  form  of  the  telescope  constructed  by  Jansen,  and  improved  by 
Galileo  ;  on  which  account  it  is  called  the  Galilean  telescope.  In  the  cut,  the  two  lenses 
are  represented  as  fastened  to  a  board,  as  first  exhibited  by  Jansen. 

690.  The  common  astronomical  telescope  consists  of  two 
glasses — viz.,  a  large  double-convex  lens  next  the  object,  called 
the  object-glass ;  and  a  small  double-convex  lens  or  microscope 
next  the  eye,  called  the  eye-piece.  For  the  greater  convenience  in 
using,  they  are  both  placed  in  a  tube  of  wood  or  metal,  and 
mounted  in  various  ways,  according  to  their  size,  and  the  pur- 
poses to  which  they  are  devoted. 

PLACED  IN   A  TUBB. 


A  is  the  object-glass,  B  the  eye-piece,  and  C  the  place  where  the  tube,  in  which  the  eye- 
piece is  set,  slides  in  and  out  of  the  large  tube,  to  adjust  the  eye-piece  to  the  focal  dis- 
tance. By  placing  the  lenses  in  a  tube,  the  eye  is  easily  placed  in  the  focus,  and  the 
object-glass  directed  toward  any  desired  object. 

691.  The  object-glass  of  a  telescope  is  usually  protected,  when 
not  in  use,  by  a  brass  cap  that  shuts  over  the  end  of  the  instru- 
ment ;  and  the  eye-pieces,  of  which  there  are  several,  of  differ- 


689.  Galilean  telescope?  Why  called  Galilean?  690.  How  common  astronomical 
tele-scopes  made?  Why  in  tube?  69 1.  How  object-glass  protected?  Wlvit  ssU  >f 
eye- pieced  ? 


B.G. 


14 


316 


ASTRONOMY 


REFRACTING  TELESCOPE  MOUKTBD  O2f  A  3WJ2X 


ent  magnifying  powers, 
are  so  fixed  as  to  screw 
into  a  small  movable  tube 
ID  the  lower  end  of  the 
instrument,  so  as  to  adjust 
them  respectively,  to  the 
focus,  and  to  the  eyes  of 
different  observers.  Such 
telescopes  usually  repre- 
sent objects  in  an  invert- 
ed position. 

The  adjoining  cut  represents  the 
simplest  form  of  a  mounted  refrac- 
tor. The  object-glass  is  at  A,  where 
the  -brass  cap  may  be  seen  cover- 
ing it  B  is  the  small  tube  into 
which  the  eye-piece  is  screwed,  and 
which  is  moved  in  and  out  by  the 
email  screw  C.  Two  eye-pieces 
may  be  seen  at  D — one  short  one, 
for  astronomical  observations,  and 
a  long  one,  for  land  objects.  For 
viewing  the  Sun,  it  is  necessary  to 
add  a  screen,  made  of  colored 
glass.  At  E,  a  bolt  goes  into  a 
socket  in  the  top  of  the  stand,  in 
which  it  turns,  allowing  the  tele- 
scope to  sweep  around  the  horizon ;  while  the  joint,  connecting  the  saddle  in  which  tii* 
telescope  rests  with  the  top  of  the  bolt,  allows  it  to  be  directed  to  any  point  between  the 
horizon  and  the  zenith.  But  such  stands  answer  only  for  comparatively  small  instruments. 

692.  Refracting   telescopes   are   mounted  in   various  ways. 
So  important  is  it  that  they  should  not  shake  or  vibrate,  that,  in 
most  observatories,  the  stand  rests  upon  heavy  mason-work  in 
no  way  connected  with  the  building,  so  that  neither  the  wind 
nor  the  tread  of  the  observer  can  shake  it.     They  are  then  fur- 
nished with  a  double  axis,  which  allows  of  motion  up  and  down, 
or  east  and  west ;  and  two  graduated  circles  show  the  precise 
amount  of  declination  and  right  ascension. 

They  are  often  furnished  with  clockwork,  by  which  the  telescope  Is  made  to  move 
westward  just  as  fust -as  the  Earth  turns  eastward;  so  that  the  celestial  object  being 
once  found,  by  setting  the  instrument  for  its  right  ascension  and  decimation,  or  by  the 
aid  of  the  Finder — a  small  telescope  attached  to  the  lower  end  of  the  large  one — it  may 
be  kept  in  view  by  the  clockwork  for  any  desirable  length  of  time.  A  telescope  thus  fur- 
nished with  right  ascension  and  declination  circles  is  called  an  Equatorial,  or  is  said  to 
be  equatoriall/y  mounted,  because  it  sweeps  east  and  west  in  the  heavens  parallel  to  the 
equator. 

693.  The  object-glasses  of  telescopes  are  not  always  made  of 
a  single  piece  of  glass.     They  may  be  made  of  two  concavo-con- 
vex glasses,  like  two  watch  crystals,  with  their  concave  sides 

692.  How  refractors  mounted,  and  why?  When  equatorial,  and  why?  698.  Ilov 
Object-glasses  made?  What  a  leruif  A  Barlow  lens? 


TELESCOPES REFRACTORS    AND    REFLECTORS.         317 

towards  each  other,  or  with  a  thin  double  concave  glass  between 
-them.     They  are  thus  double,  or  triple  ;  but  when  thus  con- 
structed, the  whole  is  called  a  lens,  as  if  composed  of  a  single 
piece. 

Lenses  have  also  been  formed  by  putting  two  concavo-conveT  glasses  together,  and 
•filling  the  space  between  them  with  some  transparent  fluid.  These  are  called  Barlow 
lenses,  from  Prof.  Barlow,  their  inventor. 

694.  As  a  prism  analyzes  the  light,  and  exhibits  different 
colors,  so  a  double  convex  lens  may  analyze  the  light  that  falls 
near  its  circumference,  and  thus  represent  the  outside  of  the 
heavenly  bodies  as  colored.     But  this  defect  is  remedied  by 
using  discs  made  of  different  kinds  of  glass,  so  as  to  correct  one 
refraction  by  another.     Refracting  telescopes  thus  corrected  are 
called  Achromatic  telescopes. 

Achromatic  is  from  the  Greek  a  chroma,  which  signifies  destitute  of  color.  Most 
refracting  telescopes  are  now  so  constructed  as  to  be  achromatic. 

695.  It  is  but  recently  that  any  good  refracting  telescopes 
have  been  made  in  this  country.     The  best  have  formerly  been 
made  in  Germany  and  France ;  but  a  number  of  very  fine  instru- 
ments have  been  made  in  this  country,  most  of  them  by  Mr. 
Henry  Fitz,  Jun.,  formerly  of  New  York  City.     Several  very 
good  instruments  have  also  been"  made  by  Alvan  Clark,  Esq.,  of 
Boston,  and  others  still  by  Charles  A.  Spencer,  Esq.,  of  Troy, 
N.  Y.     Mr.  Fitz  died  in  New  York,  November  27,  1863. 

1.  The  author  was  personally  well  acquainted  with  Mr.  Fitz,  and  during  his  life  gave 
favorable  descriptions  of  his  instruments  in  these  pages,  and  did  all  that  he  could  to 
make  his  capabilities  known  to  the  American  public.     He  made  his  first  telescope  in 
1835.    In  the  Winter  ot  1844  he  invented  a  method  of  perfecting  object-glasses  for  refract- 
ing telescopes,  making  the  first  one  of  the  bottom  of  an  ordinary  tumblor.     In  the  Fall 
of  1845  he  exhibited,  at  the  Fair  of  the  American  Institute,  an  instrument  of  6  inches 
aperture,  which,  although  made  of  common  American  material,  in  the  way  of  flint  glass, 
was  a  very  excellent  instrument    Continually  progressing  in  size,  he  finally  succeeded  in 
making  instruments  of  16  inches  aperture,  one  of  which  is  now  in  the  possession  of  Mr. 
Van  Duzee,  of  Buffalo,  N.  Y.    He  made  two  of  13  inches— one  for  the  Dudley  Observa- 
tory, at  Albany,  and  the  other  for  an  association  of  gentlemen,  at  Alleghany  City,  Pa. 
Of  12  inches  aperture,  he  produced  one  for  the  Observatory  at  Ann  Arbor,  Michigan,  and 
another  for  the  Vassar  Female  College.    He  made  for  M.  L.  Rutherford,  of  New  York. 
at  various  times,  telescopes  of  4,  5J,  6," 9,  and  11 J  inches  aperture ;  the  last,  an  instrument 
of  remarkable  defining  power,  is  now  mounted  in  Mr.  Rutherford's  Observatory,  in 
Eleventh  Street,  New  York  City.     Mr.  Vickers,  of  Baltimore,  has  a  10-inch.     Several 
of  the  size  of  8  and  9  inches  are  scattered  over  the  country.    The  British  Charg6  d1  Af- 
faires at  Montevideo  has  a  9-inch.    Mr.  Campbell,  of  New  York,  has  an  8-inch.    Of  a 
large  number  of  6  inches  aperture,  one  very  fine  instrument  was  ordered  by  the  United 
States  Government,  for  Lieut.  Gillies's  expedition  to  Chili ;  it  is  still  in  the  Observatory 
of  the  Chilian  Government     At  about  the  same  time,  he  made  another  of  the  same  size 
for  Mr.  Robert  Van  Arsdale,  of  Newark.  N.  J.    Mr.  Thomas  F.  Harrison,  Principal  of  the 
Public  Grammar  School  in  Greenwich  Avenue,  New  York,  has  another  mounted  on  that 
building. 

2.  For  a  list  of  telescopes  in  this  country,  with  the  names  of  their  respective  makers, 
focal  length,  size  of  object-glasses,  &c.,  see  table  on  subsequent  page. 

695.  What  said  of  the  manufacture  of  telescopes.?  What  other  Americans  have  miido 
them  ?  (What  said  of  Mr.  Fitz  ?  Telescopes  ?) 


318 


ASTRONOMY. 


RUTHKEFOED'S  EQUATORIAL  EEFBACTOU. 

696.  The  above  cut  represents  an  equatorial  telescope  manu- 
factured by  Mr.  Henry  Fitz,  of  New  York — the  one  used  by 
the  author  in  making  most  of  his  observations.  Its  object- 
glass  is  six  inches  in  diameter,  and  its  focal  length  eight  feet. 
It  is  perfectly  achromatic,  and  performs  all  the  tests  laid  down 
in  Dick's  Practical  Astronomer,  as  evidence  of  a  good  instru- 
ment, with  perfect  ease.  Under  favorable  circumstances,  it 
shows  the  sixth  star  in  the  trapezium  of  Orion,  and  to  show 
Polaris  double  is  a  very  easy  test  indeed. 

A  Finder  is  seen  attached  to  the  lower  end  of  the  large  instrument  It  takes  in  a 
larger  field  of  view  in  the  heavens  than  the  latter,  and  enables  the  observer  to  look  uu 
objects  with  facility,  and  bring  them  into  the  field  of  the  larger  instrument. 


REFRACTING    TELESCOPES. 


319 


THB  PHILADELPHIA  REFRACTOR.* 

697.  This  instrument  is  located  in  the  Observatory  of  the  High- 
School  of  Philadelphia.  Its  focal  length  is  eight  feet,  and  its 
aperture  six  inches — the  same  as  the  one  on  the  preceding  page. 
It  was  made  by  Merz  &  Mahler,  of  Munich,  and  cost  $2,200. 

*  We  are  indebted  to  the  courtesy  of  Messrs.  Harper  Brothers,  of  New  York,  fo- 
copies  of  several  of  these  cuts  from  their  Monthly  Magazine  for  June,  1856. 

C97  The  Philadelphia  refractor?    Size?    By  whom  made?    Cost? 


320 


ASTROXOMY. 


HAMILTON   COLLEGE  E.WBACTOK. 


.21.11 


698.  This  instrument  has  a  focal  length  of  sixteen  feet,  with 
an  object-glass  thirteen-and-a-half  inches  in  diameter.  Its  focal 
length  is  therefore  about  four  feet  less  than  is  usaal  in  the  Mu- 
nich instruments  of  the  same  aperture.  The  flint  and  crown 
glass  discs  for  it  were  imported  from  Germany,  and  the  instru- 
ment was  made  by  Messrs.  Spencer  &  Eaton,  of  Canastota,  N.  Y., 
at  a  cost  of  $10,000.  It  is  reported  to  be  a  very  superior  tele- 
scope, and,  in  workmanship,  is  regarded  as  fully  equal  to  the 
Munich  instruments. 


698.  Size  of  the  Hamilton  College  telescope? 
whom  made?    Cost? 


What  peculiarity  as  to  length?    By 


REFRACTING    TELESCOPES 


321 


GREAT   REFRACTING   TBLE8COPE   AT   CINCINNATI,   OHIO. 

699.  The  above  cut  represents  one  of  the  best  telescopes  in 
the  United  States.  It  is  located  in  the  observatory  on  Mount 
Adams,  near  Cincinnati,  Ohio,  and  was  for  several  years  under 
the  direction  of  the  late  Prof.  O.  M.  Mitchel,  by  whose  instru- 
mentality it  was  purchased  and  mounted. 

The  object-glass  is  about  12  inches  in  diameter,  with  a  focal  distance  of  17  feet  li 
was  purchased  in  Munich,  Germany,  in  1844,  at  an  expense  of  nearly  ten  thousand 
dollars. 


699.  Cincinnati  refractor— where  located?    By  whom  purchased ?    (Where?    When? 
Cost  ?    Size  and  focal  distance  ?) 


322 


ASTRONOMY. 


THB  BQUATOBIAL  BEFBACTOE  AT  ALBANY,   N.   T. 

TOO.  This  superb  instrument  is  mounted  in  the  Dudley  Ob- 
servatory, at  Albany,  and  is  one  of  the  most  important  instru- 
ments in  America.  Its  focal  length  is  15  feet  2  inches.  The 
object-glass,  made  by  the  late  Henry  Fitz,  of  New  York,  is  13 
inches  clear  aperture,  and  the  tube  is  of  mahogany,  constructed 
by  glueing  together  strips  of  about  an  inch  in  width.  A  finder, 
or  small  telescope  for  finding  objects,  is  seen  attached  to  the 
lower  end  of  the  large  instrument. 


700.  Where  located?    Size?    Bj  -whom  made  ?    What  said  of  tube?    Finder  t 


REFRACTING    TELESCOPES. 


323 


THE   GREAT    EQUATORIAL  REFRACTOR   AT   CAMBRIDGE     MASS. 

701.  This  is  probably  the  best  ins  mment  in  the  United  State*. 
Its  object-glass  is  15  inches  in  diameter,  with  a  focal  length  of 
22  feet  6  incnes.  It  has  eighteen  different  powers,  ranging  from 
103  to  2,000.  It  was  made  by  Merz  &  Mahler,  of  Munich,  Ba- 
varia, and  cost  $19,842. 

The  cut  shows  the  opening  in  the  revolving  dome  of  the  observatory,  and  the  observer 
In  his  chair  at  the  eye-piece. 


701.  Comparative  value?    Siz£?    Magnifying  powers?    By  whom  made?    (Jest  of 
Instrument? 


321 


ASTRONOMI', 


THB   OBEA1    CKAI&   TbLESCOPE,   WAND8WOKTU   COMMON,   NKAE    LONDON. 


702.  This  is  the  largest  refracting  telescope  ever  constructed 
The  object-glass  is  two  feet  in  diameter,  with  a  focal  distance  of 
76  feet.  The  tube  is  of  heavy  sheet  iron,  and  shaped  somewhat 
like  a  cigar.  It  is  13  feet  in  circumference  in  the  largest  pla^e, 
and  weighs  about  three  tons. 

This.telescope  is  suspended  from  a  brick  tower,  65  feet  high,  15  feet  in  diameter,  and 
weighing  220  tons.  The  top  of  the  tower,  from  which  the  telescope  is  suspended,  re- 
volves ;  and  by  a  chain  running  over  pulleys,  and  a  weight  and  windlass,  it  is  balanced, 
and  raised  or  lowered.  The  lower  end  rests  on  a  small  carriage,  that  runs  upon  a  circi.- 
lar  railroad  around  the  tower,  at  the  distance  of  52  feet  from  its  center.  By  these  means 
it  is  directed  to  almost  any  point  in  the  heavens.  It  is  called  the  "  Craig"  telescope,  in 
honor  of  the  Rev.  Mr.  Craig,  under  whose  direction,  and  at  whose  expense,  it  was  con- 
ttructed.  It  is  located  at  Wandsworth  Common,  near  London. 


71/2.  Describe   the   Craig  telescope.     Object  glass  ?     Focal  distance  ? 
mounted?     Why  ••ailed  "  f>aig"  telescope  f    Where  located  ? 


T  •  be  ?    How 


TRANSIT   INSTRUMENTS.  325 


A   TRANSIT   IJV8TKTTMENT. 

703.  A  Transit  Instrument  is  a  telescope  used  for  observing 
the  transits  of  celestial  objects  across  the  meridian,  for  the  pur- 
pose of  determining  differences  of  right  ascension,  or  obtaining 
correct  time.  They  are  usually  from  six  to  ten  feet  long,  and 
are  mounted  upon  a  horizontal  axis,  between  two  abutments  of 
mason-work ;  so  that  the  instrument,  when  horizontal,  will  point 
exactly  to  the  south.  It  will  then  take  objects  in  the  heavens, 
when  they  are  exactly  on  the  meridian. 

The  Transit  Instrument  and  Mural  Circle  have  been  combined 
in  one  instrument,  called  a  Meridian  Circle,  as  shown  on  a  sub- 
sequent page. 

Let  A  D  in  the  cut  represent  the  telescope,  and  E  and  W  the  east  and  west  abutments, 
between  which  it  is  placed.  On  the  left  is  seen,  attached  to  the  mason  work,  a  graduated 
circle;  and  on  the  eastern  end  of  the  axis  of  the  telescope  is  seen  an  arm,  TJ,  extending 
to  the  circle,  as  an  index.  Now,  suppose  the  index  n  to  be  at  0,  in  the  upper  part  of  the 
circle,  when  the  telescope  is  horizontal ;  then  if  the  meridian  altitude  of  the  object  to  bo 
taken  is  10%  the  index  must  be  moved  10°  from  0,  as  the  degrees  on  the  circle  and  the 
altitude  of  the  object  will  correspond. 


703.  What  is  a  transit  instrument?  Size?  How  mounted?  Describe  parts  as  shown 
in  the  cut.  llow  set  the  instrument  for  the  altitude  of  a  star?  What  combination 
nj>oken  off 


326 


ASTRONOMY. 


TRANSIT  INSTRUMENT,  WASHINGTON,  D.  C. 

704.  This  instrument  is  located  in  the  National  Observatory, 
at  Washington,  D.  C.  It  is  mounted  upon  piers  of  granite,  which 
rest  firmly  upon  a  foundation  of  stone,  extending  ten  feet  below 
the  surface  of  the  ground.  The  object-glass  was  furnished  by 
Merz  &  Mahler,  and  the  instrument  was  constructed  by  Ertel  & 
Son,  Munich.  The  entire  cost  was  $1,480. 

704.  Whore  located?    How  mounted ?    By  whom  mad??    Gout? 


TRANSIT    INSTRUMENTS. 


327 


KBRTDTAN  CIRCLE  AT  ALBANY,  JT.  T. 

705.  This  is  a  superior  transit  instrument,  with  a  mural  circle 
attached.  It  is  located  in  the  east  wing  of  the  Dudley  Observa- 
tory, at  Albany,  N.  Y.,  and  rests  upon  piers  of  Lockport  lime- 
stone, which  rest  upon  a  bed  of  sand  and  gravel,  some  ten  feet 
below  the  floor  of  the  cellar.  Taken  as  a  whole,  it  is  probably 
the  best  transit  instrument  in  the  United  States. 

1.  A  Mural  Circle  is  a  large  graduated  circle,  with  a  telescope  crossing  its  center,  used 
for  the  measurement  of  the  altitudes  and  zenith  distances  of  the  heavenly  bodies,  at  the 
instant  of  their  crossing  the  meridian.  They  are  usually  fixed  upon  a  horizontal  axis, 
that  turns  in  a  socket  firmly  fixed  in  a  north  Aid  south  wall.  The  degrees,  minutes, 
and  seconds  on  the  circle  are  read  by  means  of  microscopes,  and  indicate  the  altitude 
of  the  object.  The  Mural  Circle  and  a  transit  instrument,  as  now  combined,  are  called 
a  Meridian  Circle. 


T05.  Where  located?    How  mounted?    Comparative  importance?    What  is  a  Mitral 
?    How  combined?    What  called  ? 


Circle  t    Use?     How  usualh  mounted 


328  ASTRONOMY. 

2.  The  old  Mural  Circle  is  now  being  rapidly  superseded  by  the  Meridian  Circle  in 
the  best  observatories. 

706.  A  Comet  Seeker  is  a  re-  A  COMET  SEEKER. 
fracting  telescope  with   a  large 

aperture  and  short  focal  distance. 
As  comets  cannot  be  found  by 
their  right  ascension  and  declina- 
tion, but  often  have  to  be 
searched  up,  by  sweeping  around 
the  heavens  with  a  telescope,  be- 
fore they  became  visible  to  the 
naked  eye,  it  is  important  to 
have  telescopes  that  will  cover 
considerable  space — that  is,  of 
wide  aperture  and  short  focal  distance.  Such  a  telescope  was 
made  by  Mr.  Fitz  for  Miss  Mitchel,  of  Newport,  R.  I. 

Miss  Mitchel  is  an  amateur  astronomer,  and  has  the  honor  of  having  discovered  a  num- 
ber of  new  comets. 

707.  An  Astronomical  Clock  is  a  clock  adapted  to  keep  exact 
sidereal  time.     Taking  the  vernal  equinox  in  the  heavens  as  the 
zero  point,  and  reckoning  24  hours  eastward  to  the  same  point 
again,  the  time — reckoning  15°   to   an  hour — when  an  object 
crosses  the  meridian,  will  always  represent  the  right  ascension 
of  the  object.    Hence  right  ascension  is  usually  given  in  hours, 
minutes,  and  seconds ;  or  in  time  by  the  astronomical  clock,  set 
by  the  vernal  equinox. 

Professor  Mitchel,  we  believe,  made  some  valuable  improvements  in  astrononrcal 
clocks.  A  very  fine  instrument  of  this  kind  is  located  in  the  Dudley  Observatory,  at 
Albany,  N.  Y. 

REFLECTING    TELESCOPES. 

708.  The  Reflecting  Telescope  is  one  in  which  the  light  is  con- 
verged to  a  focus  by  means  of  a  concave  metallic  reflector  or 
speculum.     Like  the  Refractors,  they  may  be  constructed  with 
very  little  mounting ;  though  for  convenience  in  use,  it  is  neces- 
bary  to  place  the  reflector  in  a  tube. 

The  student  should  fully  understand  the  difference  between  the  two  kinds  of  tele- 
boopes,  viz. :  refractorx  and  reflectors.  In  one  respect  they  are  alike,  as  they  both  con- 
•wrge  the  rays  of  light  to  a  focus;  but  they  do  it  by  widely  different  processes,  as  the 
following  pages  will  show. 

706.  What  is  a  comet  seeker?  Why  necessary?  707.  What  is  an  astronomical 
clock  ?  70S.  Describe  a  reflecting  telescope.  Simplest  form  ? 


DIFFERENT    KINDS    OF    TELESCOPES. 

SIMPLEST  FORM  OF  A   REFLECTING  T2L23COPK. 


329 


In  this  cut,  the  light  A  is  seen  passing  from  the  object  on  the  right,  and  falling  upon 
the  concave  surface  of  the  reflector  at  B,  from  which  it  is  reflected  back  to  a  focus,  and 
enters  the  eye  -of  the  observer  at  0.  This  telescope  has  no  eye-piece. 

708.  The  focal  distance  of  a  concave  reflector  is  equal  to  half 
the  radius  of  the  sphere  formed  by  the  concave  surface  pro- 
duced. Hence  to  grind  a  reflector  for  a  focus  of  20  feet,  it  will 
be  necessary  to  have  the  curve  that  of  a  circle  whose  radius  is 
40  feet. 

FOCAL  DISTANCE  OF  A   CONCAVE  nKFLBCTOR. 


Here  the  curve  of  the  speculum  B  is  that  of  a  circle,  whose  center 
is  0 ;  while  the  focus  of  the  speculum  is  at  D,  which  is  only  half 
the  distance  from  B  to  C. 


709.  Reflecting  telescopes  are  of  several  kinds — viz.,  the  Gre- 
rwM,  the  Newtonian,  the  Casscgranian,  the  Herschdian,  &c. 
The  Gregorian  Rejkdor  has  an  aperture  in  the  center  of  the 
speculum,  and  a  small  concave  mirror  in  the  focus  of  the  specu- 
uin,  which  reflects  the  light  back  through  the  aperture  to  the 
eye-piece.  In  this  way  the  observer  is  enabled  to  face  the 
object,  and  to  direct  the  telescope  toward  it,  as  if  it  were  a 
refractor. 


708.  Focaj  distance?        709.  How  many  kinds  of  reflectors?    Describe  the  Gregorian. 
Why  colled  Gregorian? 


330 


ASTRONOMY. 


QkKGOKlAN   I'.EKLKCTOR. 


Here  the  light  A  falls  upon  the  speculum  at  B,  and  is  reflected  back  to  the  small  mir- 
ror C,  by  which  it  is  thrown  out  through  the  aperture  in  the  speculum,  to  the  eje  of  tho 
observer  at  D.  The  object  is  supposed  to  be  off  on  the  right,  in  the  direction  towards 
which  the  instrument  is  pointed.  It  is  called  a  Gregorian  telescope,  after  Mr.  Jamea 
Gregory,  who  first  suggested  the  construction  of  reflecting  telescopes. 

7 10.  The  Newtonian  Reflector  is  so  called  after  Sir  Isaac 
Newton,  its  inventor.  Instead  of  a  concave  mirror  in  the  focus 
of  the  speculum,  he  placed  a  plane  mirror  there,  inclined  so  aa 
to  reflect  the  light  to  the  side  of  the  tube,  where  it  was  received 
by  the  observer. 

NEWTONIAN   REFLECTOR. 


The  light  fron  the  speculum  is  here  shown  falling  upon  the  inclined  mirror  in  the  cen- 
ter, and  reflected  out  to  the  eye  of  the  observer. 

711.  The  Cassegranian  Rejiecior  is  so  called  from  M.  Casse- 
grain,  its  inventor.  It  resembles  the  Gregorian,  except  that  the 
speculum  placed  in  the  focus  of  the  reflector  is  convex  instead  of 
concave. 

The  Herschelian  Reflector  differs  from  all  others,  in  having  no 
small  reflector  whatever  ;  the  light  being  reflected  back  to  a 
focus  at  the  top  of  the  telescope,  and  near  the  edge  of  the  tube, 
where  the  eye-piece  is  placed,  and  where  the  observer  sits  look- 
ing into  the  mirror  with  his  back  to  the  object. 

HERSCHELIAN  TELESCOPE. 


Here  the  concave  speculum  is  seen  to  be  inclined  a  little  to  the  lower  side  of  the  tube, 
so  that  the  parallel  rays  A  are  reflected  back  to  the  observer  at  B,  at  the  fide  of  the 
instrument,  where  the  eye-piece  is  placed. 

710.  Newtonian  reflectors?       Til.  Cassegranian  ?     Difference?    ilerscheliau  ? 
eye-piece?    How  observer  sit ? 

14* 


DIFFERENT    KIXDS    OF    TELESCOPES. 


331 


712.  The  first  telescope  constructed  upon  this  plan  was  that 
by  Sir  William  Herschel,  in  1782.  This  was  called  his  20  feet 
reflector,  and  was  the  instrument  with  which  he  made  many  of 
his  observations  upon  the  double  stars.  In  1789,  he  completed 
his  forty  feet  reflector,  until  recently  the  largest  telescope  ever 
constructed. 


Bin  WILLIAM  HERSCHEL'S  FORTY  FEET  UUPLEUTOU. 


713.  The  speculum  of  this  instrument  is  4  feet  in  diameter,  3|- 
inches  thick,  and  weighed,  before  being  ground,  2,118  pounds. 

712.  First  Herschelian  telescope  ?    What  called?    Next?    713.  Herschel's  forty  feet 
reflector  ?    Size  of  Speculum  ?    Weight  ?    Tube  ?  Length  and  Weight  ?    How  mounted  ? 


332  ASTRONOMY. 

The  tube  is  made  of  sheet  iron  riveted  together,  and  painted 
within  and  without. 

The  length  of  the  tube  is  39  feet  4  inches,  and  its  weight  8,260  pounds.  It  is  elevated 
or  lowered  by  tackles,  attached  to  strong  frame-work  ;  and  the  observer,  who  sits  in  a 
chair  at  the  upper  end  of  the  tube,  and  looks  down  into  the  reflector  at  the  bottom,  \a 
raised  and  lowered  with  the  instrument.  Three  persons  are  necessary  o  use  this  tele- 
scope one  to  observe,  another  to  work  the  tube,  and  a  third  to  note  down  the  observa- 
tions. A  speaking  tube  runs  from  the  observer  to  the  house  where  the  assistants  are  at 
work  By  this  telescope,  the  sixth  and  seventh  satellites  of  Saturn  were  discovered ; 
and  it  was  the  chief  instrument  used  by  its  distinguished  owner,  in  making  the  observa- 
tions and  discoveries  which  have  immortalized  his  name,  and  which  have  so  abundantly 
enriched  and  advanced  the  science  of  astronomy. 

LORD    ROSSK'S   GREAT    RKFLECTINO    TELES^)PB. 


714.  This  is  the  largest  reflecting  telescope  ever  constructed. 
The  speculum,  composed  of  copper  and  tin,  weighed  three  tons  as 
it  came  from  the  mould,  and  lost  about  -Jth  of  an  inch  in  grinding. 
It  is  5£  inches  thick,  and  6  feet  in  diameter.  It  was  cast  on 
the  13th  of  April,  1842,  and  was  cooled  gradually  in  an  oven  for 
16  weeks,  to  prevent  its  cracking,  by  a  sudden  or  unequal  reduc- 
tion of  the  temperature.  This  speculum  has  a  reflecting  surface 
of  4071  square  inches.  The  tube  is  made  of  deal  wood,  one 
inch  thick,  and  hooped  with  iron.  Its  diameter  is  seven  feet, 
and  its  length  56. 

The  entire  weight  of  this  telescope  is  twelve  tons.  It  is  mounted  between  two  north 
and  south  walls,  24  feet  apart,  72  feet  long,  and  48  feet  high.  The  lower  end  rests  upon 
an  universal  hinge.  It  can  be  lowered  to  the  horizon,  and  raised  to  the  zenith,  and 
lowered  northward  till  it  takes  in  the  Pole  Star. 

Observer  where?    Usefulness?        7J4.  Lord  Rosse's  telescope?    Weight  of  speculum? 
Diameter?     Thickness?     Cooling?     Tube?     Entire  weight?     How  mounted?     What 


OBSERV ATOPIES  AND  TELESCOPES. 


333 


OBSKRVATOEIES  AND  TELESCOPES  IN   THE  TTNIT1D  STATES. 


THEI] 

I  TELE8C< 

>PE8. 

OBSERVATORIES. 

When 
procured. 

Name  of 
maker. 

Focal 
length. 

Aperture  of 
object  glass. 

Cost. 

Tale  College  

1830 

Dollond 

ft.   in. 
10    — 

inches. 
5 

$1  000 

Wesleyan  University 

1836 

7 

6 

1  000 

Williams  College.  

(1836 

Holcomb. 

10    — 

reflector. 

Hudson,  Ohio. 

)  1852 
1837 

A.  Clark. 

5      6 

7 
4 

Philadelphia 

1840 

8      4 

Af. 

1  900 

West  Point 

1841 

g 

6 

Washington  ;  .  . 

1844 

Merz 

15      3 

9-6 

6000 

Cincinnati      ....           .... 

17    — 

12 

9437 

Cambridge                ... 

1846 

M 

22      6 

15 

19  842 

Dartmouth  College 

1848 

H 

g 

6'4 

Georgetown  

1849 

Simms 

7      6 

4-8 

1  600 

Erskine  

Fitz 

7    — 

5'6 

1  050 

Shelby 

1850 

Merz 

10      4 

7-5 

8500 

Columbia  (S.  C.)  College  

1851 

Fitz. 

8      4 

64- 

l'200 

Columbia  (Mo.)  

1852 

5    — 

4 

225 

Friends,  Philadelphia 

1846 

H 

7    — 

5 

Amherst  College 

1854 

Clark. 

8      6 

7i 

1  800 

Michigan  University  

1853 

Fitz 

17    — 

12i 

e'ooo 

Dudley,  Albany,  NY... 

1857  ? 

15      2 

13 

14500 

Hamilton  College 

1857 

16    — 

13i 

10  000? 

J.  Jackson,  near  Philadelphia.  .  . 
Mr.  Longstreet,  Philadelphia  
8.  G.  Gurnmere,  Burlington,  N.  J. 

B.  Vanarsdale,  Newark,  N.  J  

W.  8.  Van  Duzee,  Buffalo,  N.  Y.  . 
W.  S.  Dickie  Elkton  Ky. 

1846 

1847 
J1850 
j  1851 

Fit! 

It 

8      4 
7    — 
5    — 
7    — 
8      4 
11    — 
6    — 

63-10 
5 
4 
5 

if 

*i 

L833 
900 
425 
750 
1.000 
2,220 
300 

D.  Mosman,  Bangor,  Me  
J.  Campbell,  New  York  

1852 

" 

5    — 
10    — 

4 
8 

225 
1,150 

L.  M.  Kutherford,  New  York  .... 

" 

9      6 

9 

2.200 

FOBEIGN   OBSEKVATOKIES— THEIR   LATITUDE   AND   LONGITUDE. 


OBSERVATORIES. 


Longitude  in  Time. 


Altona 

Armagh 

Berlin 

Brussels 

Cambridge 

Cape  of  Good  Hope. 

Copenhagen  

Dorpat 

Dublin 

Edinburgh. 

Gottingen 

Greenwich 

Konigsberg 

Munich 

Palermo 

Paris 

Petersburg 

Rome 

Turin 

Vienna 


82  '    45 

21 

80 

51 

12 

56 

40       53 

22 

23 

51 

31 

23 

42 

8      45 
6      44 

50       13 

56 

53 


h.    m. 


N. 

12.7      N. 
16.7      N. 

10.7  N. 

51.8  N. 
3          S. 

N. 

47.1  N. 
13          N. 

23.2  N. 

47.9  N. 
88.2      N. 
50.4      N. 

N. 
N. 
N. 


29.7      N. 
54         N. 

N. 


6 

85.5      N. 


88 

20 
68 
IT 
0 
18 
50 
46 
25 
12 
39 
0 

22 
0  46 
0  53 
0  9 
2  1 
0  49 
0  30 


s. 

46.2 
35.5 
34.9 
27.2 
23.5 
56.0 
19.3 
54.6 
22 
43.0 
46.8 
0.0 
0.4 
25.4 
25.5 
21.5 
13.5 
54  7 
48.4 
32.6 


E. 
E. 
E. 
E. 
E. 
E. 
W. 

E.' 

E. 
E. 
E. 
E. 
E. 
E. 
E. 
E. 


699.  Public  observatories  in  this  country?     Largest  telescope ?       Table?        PrivciO 
obser  vatories— names  ?    Telescopes— by  whom  mostly  m»de  ?    What  other  table  ? 


334:  ASTRONOMY. 

CHAPTER    XX. 
PROBLEMS    AND    TABLES. 

PROBLEM     I. 
TO    CONVERT   DEGREES,    ETC.,  INTO    TIME. 

RULE  I — Divide  the  degrees  by  15,  for  hours ;  and  multiply  thi 
lemainder,  if  any,  by  4,  for  minutes. 

2.  Divide  the  odd  minutes  and  seconds  in  the  same  manner  b; 
15  for  minutes,  seconds,  &c.,  and  multiply  each  remainder  by  4 
for  the  next  lower  denomination. 

EXAMPLE  1.— Convert  32°  34'  45"  into  time. 

Thus,  32°-f-15:=2h.     8' 

34  -M5  =  2     16* 

45  -v-15=r  3 


Ans.     32°  34'  45*=2h.  10'  19* 

EXAMPLE  2. — If  it  is  12  o'clock  at  this  place,  what  is  the  tim< 
20°  east  of  us  ? 

Thus  fifteen  in  20°,  once,  and  five  over ;  the  once  is  1  hour 
and  the  5  multiplied  by  4,  gives  20  minutes ;  the  time  is  thei 
1  hour  and  20  minutes  past  12. 

EXAMPLE  3. — The  longtitude  of  Hartford  is  72°  50'  west  o 
Greenwich;  what  time  is  it  at  Greenwich  when  it  is  12  o'clock  a 
Hartford  ?  Ans.  4h.  51m.  20s. 

EXAMPLE  4. — When  it  is  12  o'clock  at  Greenwich,  what  is  th< 
time  at  Hartford  ?  Ans.  7h.  8m.  40s. 


PROBLEMS    AND   TABLES.  335 

PROBLEM   II. 
TO    CONVERT    TIME    INTO    DEGREES,  ETC. 

RULE. — Multiply  the  hours  by  15,  and  to  the  product  add  one- 
fourth  of  the  minutes,  seconds,  <fec.,  observing  that  every  minute 
of  time  makes  £°,  and  every  second  of  time  \'. 

EXAMPLE  1. — In  2  hours,  10  minutes,  and  19  seconds;  how 
many  degrees? 

Thus;  ~~  2h.  10m.     19. 

15 

305 

Add  10  quarters,  or  |  of  the  min.       2      30' 
Add  19  quarters,  or  £  of  the  sec.  4         45' 

Ans.     32°    34'       45* 

Ex.  2. — When  it  is  12  o'clock  at  Hartford,  it  is  4  hours,  51 
minutes,  and  20  seconds  past  noon  at  Greenwich ;  how  many 
degrees  is  Hartford  west  of  Greenwich  ? 

Thus :  15  times  4  is  60— added  to  £  of  51,  is  72°  45ff,  and 
this  increased  by  \  of  20,  is  72°  50'.  Ans. 

Ex.  3. — A  Liverpool  packet,  after  sailing  several  days  from 
New  York,  finds  the  time  by  the  Sun  2  hours  and  40  minutes 
later  than  by  the  ship's  chronometer  :  how  far  has  the  ship  pro- 
giessed  on  her  way  ? 

Ex.  4. — A  vessel  leaves  Boston,  and  having  been  tossed  about 
in  foul  weather  for  some  days,  finds,  that  when  it  is  12  o'clock 
by  the  Sun,  it  is  only  11  o'clock  and  50  minutes  by  the  watch  ; 
is  the  vessel  east  or  west  of  Boston  ;  and  how  many  degrees  ? 

Ex.  5. — The  moment  of  greatest  darkness,  during  the  annular 
eclipse  of  1831,  took  place  at  New  Haven,  10  minutes  after  1 
o'clock.  A  gentleman  reports  that  it  happened  precisely  at  1, 
where  he  observed  it ;  and  another  that  it  was  5  minutes  after 
1  where  he  saw  it ;  Query.  How  far  east  or  west  were  these 
gentlemen  from  each  other,  and  how  many  degrees  from  New 
Haven  ? 


336  ASTEONOMY. 

PROBLEM   III. 

TO  FIND  WHAT    STARS  ARE    ON   THE  MERIDIAN  AT  NINE  O'CLOCK  IJ 
THE  EVENING  OF  ANY  GIVEN  DAT. 

RULE. — Look  for  the  given  day  of  the  month,  at  the  botton: 
of  the  maps,  and  all  the  stars  having  the  same  degree  of  righl 
ascension  will  be  on  the  meridian  at  that  time. 

EXAMPLE  1. — What  stars  will  be  on  the  meridian  at  9  o'clock 
the  19th  of  January? 

Solution. — On  Map  III.  I  find  that  the  principal  stars  stand- 
ing over  against  the  19th  of  January,  are  Rigel  and  Capella. 

Ex.  2. — What  stars  are  on  the  meridian  the  20th  of  Decem- 
ber ?  Ans.  Menkar  and  Algol. 


PROBLEM    IV. 
ANY  STAR  BEING  GIVEN,  TO  FIND  WHEN  IT  CULMINATES. 

RULE. — Find  the  star's  right  ascension  in  the  table,  or  by  the 
map  (on  the  equinoctial),  and  the  day  of  the  month  at  the  top 
or  bottom  of  the  map  will  be  the  day  on  which  it  culminates  at 
9  o'clock. 

EXAMPLE  1. — At  what  time  is  the  bright  star  Sirius  on  the 
meridian  ? 

Solution. — I  find  by  the  table,  and  by  the  map,  that  the  right 
ascension  of  Sirius  is  6 -hours  and  about  38  minutes;  and  the 
time  corresponding  to  this,  at  the  bottom  of  the  map  is  the  llth 
of  February. 

Ex.  2. — At  what  time  is  Alpheratz,  in  the  head  of  Andromed^ 
on  the  meridian  ?  Ans.  The  9th  of  November. 


PROBLEMS   AND   TABLES.  337 

PROBLEM    V. 

THE  J1IGHT  ASCENSION  AND  DECLINATION  OF  A  PLANET  BEING 
GIVEN,  TO  FIND  ITS  PLACE  ON  THE  MAP. 

RULE. — Find  the  right  ascension  and  declination  of  the  planet 
on  the  map,  and  that  will  be  its  place  for  the  given  day. 

EXAMPLE  1. — Venus's  right  ascension  on  the  1st  of  January, 
1833,  was  21  hours,  30  minutes,  and  her  declination  16f°  south ; 
required  her  situation  on  the  map  ? 

Solution. — On  the  right  hand  of  the  Plate  II.  I  count  off  16f° 
from  the  equinoctial,  on  the  marginal  scale  south,  and  from  that 
point,  30  minutes  to  the  left  or  just  half  the  distance  between  the 
XXI.  and  XXII.  meridian  of  right  ascension,  and  find  that 
Venus,  that  day,  is  within  two  degrees  of  Delta  Capricorni,  neai 
the  constellation  Aquarius,  in  the  zodiac. 

Ex.  2. — Mars'  right  ascension  on  the  13th  of  March,  1833,  is 
5  hours,  1  minute,  and  his  declination  24i°  north ;  required  his 
situation  on  the  map  ? 

Solution. — I  find  the  fifth  hour  line  or  meridian  of  right  ascen- 
sion on  Plate  III..,  and  counting  upward  from  the  equinoctial 
24i°,  I  find  that  Mars  is  between  the  horns  of  Taurus,  and  about 
5°  S.  W.  of  Beta  Auriga. 

Ex.  3. — Required  the  position  of  Jupiter  and  Saturn  on  the 
13th  of  February  and  the  25th  of  May? 


PROBLEM    VI. 

TO  FIND  AT  WHAT  MOMENT  ANY  STAR  WILL  PASS  THE  MERIDIAN  ON 
A  GIVEN  DAY. 

RULE. — Subtract  the  right  ascension  of  the  Sun  from  the 
star's  right  ascension,  found  in  the  tables :  observing  to  add  24 
hours  to  the  star's  right  ascension,  if  less  than  the  Sun's,  and 
the  difference  will  show  how  many  hours  the  star  culminates 
after  the  Sun. 


338  ASTRONOMY. 

EXAMPLE  1. — At  what  time  willProcyon  pass  the  meridian  on 
the  24th  of  February  ? 

Solution.— R.  A.  of  Procyon,  7h.  30m.  33s.  +  24h. 

31     30'     33* 

R.  A.  of  Sun,  24th  Feb.  22     29        1 

Ans.  1       I      32~ 

That  is  lin.  32s.  past  9  o'clock  in  the  evening. 

Ex.  2. — At  what  time  will  Denebola  pass  the  meridian  on  the 
first  of  April  ? 

Solution.—R.  A.  of  Denebola  is  llh.  40'    32* 

R.  A.  of  Sun,  April  1,  0     41     25 

Ans.        "lO     59       7~ 
That  is,  at  59  minutes,  7  seconds,  past  10  in  the  evening. 

Ex.  3. — At  what  time  on  the  first  day  of  each  month,  from 
January  to  July,  will  Alcyone,  or  the  Pleiades,  pass  the  meri- 
dian ? 

Ex.  4. — At  what  time  will  the  Dog-Star,  or  Sirius,  culminato 
on  the  first  day  of  January,  February,  and  March  1 

Ex.  5. — How  much  earlier  will  Spica  Yirginis  pass  the  meri 
dian  on  the  4th  of  July,  than  on  the  15th  of  May  ? 

Ans.  3  hours,  25  minutes. 

PROBLEM    VII. 

TO  FIND  THE  SUN'S  LONGITUDE  OR  PLACE  IN  THE  ECLIPTIC,  ON  ANY 
GIVEN  DAY. 

RULE. — On  the  lower  scale,  at  the  bottom  of  the  Planisphere 
(Map  VIII.)  look  for  the  given  day  of  the  month ;  then  the  sign 
and  degree  corresponding  to  it  on  the  scale  immediately  above  it 
will  show  the  Sun's  place  in  the  ecliptic. 

EXAMPLE  1. — Required  the  Sun's  longitude,  or  place  in  the 
ecliptic,  the  16th  of  September. 

Solution. — Over  the  given  day  of  the  month,  September  16th, 
stands  5  signs  and  23  degrees,  nearly,  which  is  the  Sun's  place  in 
the  ecliptic  at  noon  on  that  day ;  that  is,  the  Sun  is  about  23 
degrees  in  the  sign  Virgo. 


PROBLEMS  A>D  TABLES.  339 

N.B.-  If  the  5  signs  be  multiplied  by  80,  and  the  23  degrees  be  added  to  it,  it  will  give 
•Jte  loo£itude  in  degrees,  173. 

Ex.  2. — Required  the  Sun's  place  in  the  ecliptic  at  noon,  OL 
the  10th  of  March. 

PROBLEM  VIII. 

GIVEN  THE  SUN'S  LONGITUDE,  OR  PLACE  IN  THE  ECLIPTIC,  TO  FIND  HIS 
RIGHT  ASCENSION  AND  DECLINATION. 

RULE. — Find  the  Sun's  place  in  the  ecliptic  (the  curved  lice 
which  runs  through  the  body  of  the  planisphere),  and  with  a 
pair  of  compasses  take  the  nearest  distance  between  it  and  the 
nearest  meridian,  or  hour  circle,  which  being  applied  to  the  gra- 
duated scales  at  the  top  or  bottom  of  the  planisphere  (measur- 
ing from  the  same  hour  circle),  will  show  the  Sun's  right  ascen- 
sion. Then  take  the  shortest  distance  between  the  Sun's  place 
in  the  ecliptic  and  the  nearest  part  of  the  equinoctial,  and  apply 
it  to  either  the  etist  or  west  marginal  scales,  and  it  will  give  the 
Sun's  declination. 

EXAMPLE  1. — The  Sun's  longitude,  September  16th,  1833,  is 
5  signs,  23  degrees,  nearly  ;  required  his  right  ascension,  and 
declination. 

Solution. — The  distance  between  the  Sun's  place  in  the  eclip- 
tic and  the  nearest  hour  circle  being  taken  in  the  compasses,  and 
applied  to  either  the  top  or  bottom  graduated  scales,  shows  the 
right  ascension  to  be  about  11  hours  35  minutes  ;  and  the  dis- 
tance between  the  Sun's  place  in  the  ecliptic,  and  the  nearest 
pert  of  the  equinoctial,  being  applied  to  either  the  east  or  west 
marginal  scales,  shows  the  declination  to  be  about  2°  45',  which 
is  to  be  called  north,  because  the  Sun  is  to  the  northward  of 
the  equinoctial ;  hence  the  Sun's  right  ascension,  on  the  given 
day,  at  noun,  is  about  11  hours  35  minutes,  and  his  declination 
2°  45'  N. 

Ex.  2. — The  Sun's  longitude,  March  10th.  1833,  is  11  signs, 
19  degrees,  nearly  ;  required  his  right  ascension  and  declin? 
tion  ? 

Ans.  R.  A.  23h.  21m.  Deci.  4°  11'  nearly. 

PROBLEM    IX. 
TO  FIND  THE  RIGHT  ASCENSION  OF  THE  MERIDIAN  AT  ANY  5IVEN  TIME. 

RLLE. — Find  the  Sun's  place  in  the  ecliptic  by  Problem  IX. , 
and  his  right  ascension  by  Problem  X.,  to  the  eastward  of 


340  ASTRONOMY. 

which  count  off  the  given  time  from  noon,  and  it  will  show  the 
right  ascension  of  the  meridian,  or  mid-heaven. 

EXAMPLE  1. — Required  the  right  ascension  of  the  meridian  9 
hours,  25  minutes  past  noon,  September  16th,  1833  ? 

Solution. — By  Problems  IX.  and  X.,  the  Sun's  right  ascen- 
sion at  noon  of  the  given  day,  is  11  hours  35  minutes  ;  to  the 
eastward  of  which,  9  hours  and  25  minutes  (the  given  time) 
being  counted  off,  shows  the  right  ascension  of  the  meridian  to 
be  about  21  hours. 

Ex.  2. — Required  the  right  ascension  of  the  meridian  at  6 
hours  past  noon,  March  10th,  1833  ? 

Solution. — By  Problems  IX.  and  X.,  the  Sun's  right  ascension 
at  noon  of  the  given  day,  is  23  hours  and  21  minutes  j  to  tht 
eastward  of  which,  the  given  time,  6  hours,  being  counted  off, 
shows  the  right  ascension  of  the  meridian  to  be  about  5  hours, 
21  minutes. 

REMARK. — In  this  example,  it  may  be  necessary  to  observe,  that  where  the  eastern,  or 
left-hand  extremity  of  the  planisphere  leaves  off,  the  western,  or  right-hand  extremity 
begins  ;  therefore,  in  counting  off  the  given  time  on  the  top  or  bottom  graduated  scales, 
the  reckoning  is  to  be  transferred  from  the  left,  and  completed  on  the  right,  as  if  the  two 
outside  edges  of  the  planisphere  were  joined  together. 

PROBLEM    X. 

TO    FIND  WHAT    STARS    WILL    BE    ON    OR    NEAR   THE  MERIDIAN,  AT  ANY 
GIVEN  TIME. 

RULE. — Find  the  right  ascension  of  the  meridian  by  Problem 
XI.,  over  which  lay  a  ruler,  and  draw  a  pencil  line  along  its 
edge  from  the  top  to  the  bottom  of  the  planisphere,  and  it  will 
show  all  the  stars  that  are  on  or  near  the  meridian. 

EXAMPLE  1. — Required  what  stars  will  be  on  or  near  the 
meridian  at  9  hours,  25  minutes  past  noon,  Sept.  16th,  1833  ? 

Solution. — The  right  ascension  of  the  meridian  by  Problem 
XI.  is  21  hours  :  this  hour  circle,  or  the  line  which  passes  up 
and  down  through  the  planisphere,  shows  that  no  star  will  be 
directly  on' the  meridian  at  the  given  time  ;  but  that  Alderamin 
will  be  a  little  to  the  east,  and  Deneb  Cygni  a  little  to  the  west 
of  it ;  also  Zeta  Cygni,  and  Gamma  and  Alpha  in  the  Little 
Horse,  very  near  it  on  the  east. 

PROBLEM    XI. 


MULE. — As  the  Sun's  horizontal  parallax  is  to  radius,  so  if 
tue  semi-diameter  of  the  Earth  to  its  distance  from  the  Sun. 


PROBLEMS  AND  TABLES.  3il 

By  Logarithms, — As  tangent  of  the  Sun's  horizontal  parallax 
is  to  radius,  so  is  the  Earth's  semi-diameter  to  her  mean  distance 
from  the  Sun. 

8'.5776:  206264-.8 :  :3962 :  95,273,869  miles. 

£y  Logarithms, 

As  tangent  of  the  Surf's  horizontal  parallax,  8' .5776=  5.6189407 
Is  to  radius,  or  90%  =10-0000000 

So  is  the  Earth's  serai-diameter,  8962=  8.5979143 

To  the  Earth's  distance,  95,273,869=  7.9789738 

PROBLEM   XII. 

TO  FIND  THE  DISTANCE  OF   ANY  PLANET    FROM   THE  SUN,  THAT  OF  THB 
EARTH    BEING  KNOWN. 

RULE. — Divide  the  square  of  the  planet's  sidereal  revolution 
round  the  Sun,  by  the  square  of  the  Earth's  sidereal  revolution, 
and  multiply  the  cube  root  of  the  quotient  by  the  Earth's  mean 
distance  from  the  Sun. 

By  Logarithms, — From  twice  the  logarithm  of  the  planet's 
sidereal  revolution,  subtract  twice  the  logarithm  of  the  Earth's 
sidereal  revolution,  and  to  one-third  of  the  remainder,  add  the 
logarithm  of  the  Earth's  mean  distance  from  the  Sun. 

EXAMPLE. — Required  Mercury's  mean  distance  from  the  Sun,  that  of  the  Earth  being 
V5,273,S69  miles. 

Mercury's  sidereal  revolution  is  87.969258  days,  or  7600543'. 8912:  the  Earth's  sidereal 
revolution  is  865.256374417  days,  or 

3155S15V.5  7600543.9 

01558151'. 5  7600543.9 


995916962096952  25   by  which  divide   57768267575827.21 

and  the  quotient  will  be  0.052005106713292,  the  cube  root  of  which  is  0.3870977,  and  this 
multiplied  by  94,881,891,  gives  86,727,607  miles,  for  Mercury's  distance  from  the  Sun. 
This  problem  may  be  performed  by  logarithms  in  as  many  minutes  as  the  former  method 
requires  hours, 

Mercury's  Sid.  Rev.  7600543'.9  log.=6.880S447  x  2  13.7616894 

Earth's  Sid.   Rev.  31558151'.    log. = 7.4991302  *  2  14.9982604 

X)— 2.7634290 

Add  log.  of  the  Earth's  mean  distance, 

Mercury's  distance,  86,880,422.  Ans.  7.5667835 

If  the  pupil  have  not  already  learned  the  use  of  logarithms,  this  problem  will  satisfy 
him  of  their  unspeakable  advantage  over  all  other  modes  of  computation.  By  reviewing 
the  above  calculation,  he  will  perceive  that  instead  of  multyplying  31558151'.5  by  itself, 
he  need  only  multiply  its  logarithms  by  two  !  and  instead  of  extracting  the  cube  root  of 
0.058005106713292,  he  need  only  divide  its  logarithm  by  three  !  and  instead  of  multiply- 
ing 0.3870977,  by  95,273,869,  he  need  only  add  their  logarithms  together.  He  need  not 
think  himself  a  dull  scholar,  if  by  the  former  method  he  come  to  the  true  result  in  fiv* 
ttcurs;  nor  remarkably  quick,  if  by  the  latter  he  come  to  it  in^oa  minutes. 

PROBLEM   XIII. 
TO    FIND   THE    HOURLY   MOTION    OF    A   PLANET    IN    ITS    ORBIT. 

RULE. — Multiply  the  planet's  .mean  distance  from  the  Sun  by 


342 


ASTRONOMY. 


C. 28 3 1853,  and  divide  the  product  by  the  time  of  the  planet's 
sidereal  revolution,  expressed  in  hours,  and  the  decimals  of  an 
hour. 

By  Logarithms. — Add  0.7981799  to. the  logarithm  of  the 
'planet's  mean  distance  from  the  Sun,  and  from  the  sum  subtract 
the  logarithm  of  the  planet's  revolution*  expressed  in  hours. 

EXAMPLE. — Required  the  Earth's  hourly  motion  in  its  orbit. 

Log.  of  Earth's  distance=7.978073S  +  0.7981799=  8.7771587 

Subtract  hog.  of  Earth's  revolution  8.9428090 

Gives  Earth's  horary  motion,  68,288  miles,  4.834344T 

PROBLEM   XIV. 
TO    FIND   THE    HOURLY   MOTION    OF   A    PLANET    ON    ITS   AXIS. 

RULE. — Multiply  the  diameter  of  the  given  planet  by  3.14159, 
and  divide  the  product  by  the  period  of  its  diurnal  rotation. 

By  Logarithms. — Add  4.0534524  to  the  logarithm  of  the 
planet's  diameter,  and  from  the  sum  subtract  the  logarithm  of 
its  diurnal  rotation,  expressed  in  seconds. 


Earth's  diameter,  7924  log.  = 

Add  log.  of  8600' + log.  of  8.14159  =  4.0584524 

7.9523969 
Subtract  log.  diurnal  rotation,  23h.  56'  4".09  =  4.9353263 

Ana.    1040.09  miles  =  8.0170706 

PROBLEM   XV. 
TO    FIND   THE    RELATIVE    MAGNITUDE    OF   THE    PLANETS. 

RULE. — Divide  the  cube  of  the  diameter  of  the  larger  planet 
by  the  cube  of  the  diameter  of  the  less. 

By  Logarithms. — From  three  times  the  logarithm  of  the 
larger,  subtract  three  times  the  logarithm  of  the  less. 

EXAMPLE. — How  much  does  the  size  of  the  Earth  exceed  that  of  the  Moon  ? 
Earth's  diameter,  7912  log.  8.8982863  x  3=  11.6948589 

Moon's  diameter,  2160  log.  8.3343376x3=  10.0080128 

The  Earth  exceeds  the  Moon,  49.1865  times.    Ans.  1.6918461 

In  this  example,  7912  miles  is  assumed  as  the  mean  between  the  Earth's  equatorial 
and  polar  diameter :  the  former  being  7924,  and  the  latter  7898  miles. 

PROBLEM   XVI. 

TO    FIND   THE    PROPORTION    OF    SOLAR   LIGHT   AND    HEAT    AT    EACH    OF 
THE   PLANETS. 

RULE. — Divide  the  square  of  the  planet's  greater  distance 
from  the  Sun,  by  the  square  of  the  less. — Or,  subtract  twice  the 
logarithm  of  the  greater  distance  from  twice  the  logarithm  of 
the  less. 


PROBLEMS    AND    TABLES. 


343 


EXAMPLE. — How  much  greater  is  the  Sun's  light  and  -heat  at 
Mercury,  than  at  the  Earth  ? 


Log.  of  Earth's  distance 

"      of  Mercury's 
Ans.  6.6736  times. greater = 


7.9789738x2=15.9579176 

7.5667959  x  2=15.1335918 

O.S243553 


PROBLEM    XVII. 
TO    FIND    THE    CIRCUMFERENCE    OF    THE    PLANETS. 

RULE. — Multiply  the  diameter  of  the  planet  by  3.14159,  or, 
add  the  logarithm  of  the  planet's  diameter  to  0.497149 9. 

PROBLEM    XVIII. 
TO    FIND    THE    CIRCUMFERENCE    OF    THE    PLANETARY    ORBITS. 

RULE. — Multiply  the  planet's  mean  distance  from  the  Sun  by 
c. 2831853  ;  or,  to  the  logarithm  of  the  planet's  mean  distance, 
add  0.7981799,  and  the  sum  will  be  the  logarithm  of  the  answer. 

PROBLEM    XIX. 

TO     FIND    IN    WHAT    TIME  ANY  OF  THE  PLANETS  WOULD  FALL  TO  THE 
SUN,    IF    LEFT    TO    THE    FORCE    OF    GRAVITATION    ALONE. 

KULE. — Multiply  the  time  of  the  planet's  sidereal  revolution 
by  0.176776  ;  the  result  will  be  the  answer. 

By  Logarithms. — From  the  logarithm  of  the  planet's  sidereal 
revolution,  subtract  0.7525750,  and  the  remainder  will  be  the 
logarithm  of  the  answer,  in  the  same  denomination  as  the  side- 
real revolution. 

Required  the  times,  respectively,  in  which  the  several  planets  would,  fall  to  the  Sun  oy 
the  force  01  gravity. 


Planets  would  fall  to  the  Sun. 

Days.    H.    M.    S. 

Logarithms. 

Mercury, 
Venus, 
Earth, 
Mars, 
Jupiter, 
Saturn, 
Herschel, 
Moon  to  the  Earth, 

15       13     13    16 
89       17     19    22 
64       13     88    55 
121        10     86      3 
265       21     33    35 
1901       23     24      4 
5424       16     52      1 
4       19     54    57 

6.1282686 
6.5355424 
6.7465357 
7.0208817 
7.8206849 
8.2157186 
8.670S897 
5.6204459 

THE    END. 


SXPLAJSTATIONS  AND  PROBLEMS 


ADAPTED   TO 


WGITALL'S    PLANISPHERE. 


TO    BE   USED   IN   CONNECTION   WITH   THE   CELESTIAL  ATLAS. 

t 


NOTE. — This  is  a  movable  Planisphere,  invented  and  copy- 
righted by  Henry  Whitall,  and  for  sale  by  the  publishers  of  Bur- 
ritt's  GEOGRAPHY  OF  THE  HEAVENS,  exhibiting  the  stars  that  are  ris- 
ing, setting,  on  the  meridian,  or  their  position  in  the  firmament,  as 
seen  in  the  United  States  every  minute,  for  HUNDREDS  OF  YEARS. 
The  right  ascension  and  declination  of  the  sun,  moon,  stars,  and 
planets  ;  the  equation  of  time  (sun  fast  or  slow) ;  harvest-moon ; 
sun  and  moon  lunning  high  and  low;  the  milky  way,  as  it 
changes  its  course  for  every  hour ;  change  of  seasons,  &c.,  can  be 
readily  explained  with  this  invaluable  substitute  for  a  Celestial 
Globe,  "  being  as  much  better  as  it  is  cheaper"  than  that  expen- 
sive school  apparatus. 

It  is  light,  portable,  accurate,  containing  much  within  a  small 
space,  and  is  sold  for  THREE  DOLLARS,  which  price  brings  it  within 
the  means  of  all  lovers  of  science,  and  of  every  teacher  who  may 
desire  his  pupils  to  become  acquainted  with  the  wonders  of  the 
heavens.  This  knowledge  need  no  longer  be  confined  to  the 
learned  few,  for  the  use  of  this  Planisphere  will  enable  any  one  to 
become  familiar  with  the  stars  and  constellations,  and  will  prove 
pleasing  and  instructive.  The  desideratum  so  long  desired  is 
thus  supplied,  and  reading  the  stars  is  no  longer  a  mystery. 


EXPLANATIONS    AND    PROBLEMS. 

PROBLEMS. 

WHICH   MAY   BE   PERFORMED   ON   THE    PLANISPHERE. 

THE  DAY  OF  THE  MONTH,  THE  HOUR,  AND  MINUTE  BEING  GIVEN, 
TO  FIND  WHAT  STAES  ARE  RISING,  SETTING,  ON  THE  MERIDIAN, 
OR  IN  ANY  PART  OF  THE  FIRMAMENT. 

APPLICATION. — Bring  the  given  hour  and  minute  opposite  the 
given  day  of  the  month ;  hold  the  zenith  over  head,  with  the 
meridian  in  a  line  north  and  south ;  the  Planisphere  will  then 
represent  in  miniature  the  constellations  visible  in  the  heavens  at 
that  time.  The  stars  which  are  rising  are  near  the  eastern,  and 
those  setting,  near  the  western  horizon.  Thus  can  be  seen  the 
stars  in  any  part  of  the  heavens,  at  every  minute,  sufficiently 
accurate  for  most  practical  purposes. 

EXAMPLE. — Where  will  An-drom'e-da  be  at  10  o'clock  on  the  10th  of 
November?  (29.)  Ans.  Directly  over  head. 

EXAMPLE. — Where  will  the  Royal  Family  (Ce-phe'us,  Cas-si-o-pe'ia,  An- 
drom'e-da,  and  Per'se-us)  be,  at  4£  o'clock  on  the  morning  of  November  10th  ? 
Ans.  Setting  in  the  N.  W. 

EXAMPLE. — On  what  day  will  the  Royal  Family  be  setting  in  the  North- 
west at  9  o'clock,  evening  ?  Ans.  About  the  4th  of  March. 

EXAMPLE. — Where  will  $  Ursa  Major  (Megres)  be,  at  9  o'clock  on  the  10th 
cf  May?  (149.)  Ans.  On  the  meridian. 

EXAMPLE. — Where  will  fi  Leo  (Denebola)  be,  at  9  o'clock  on  the  3d  of 
May  ?  (132.)  Ans.  On  the  meridian. 

TELESCOPIC  OBJECTS. 

The  right  ascension  of  telescopic  objects  is  given  in  hours  and 
minutes.  To  find  their  place  in  the  heavens,  bring  the  hour  and 
minute  of  R.  A.  to  the  arrow,  near  March  22d,  on  the  outer  circle  ; 
under  the  declination,  marked  on  the  meridian,  will  be  the  situation 
of  the  object ;  on  the  equator,  opposite  0,  can  be  seen  the  degrees 
of  R.  A. 

Should  the  R.  A.  be  13  hours,  bring  the  arrow  to  1,  past  raid- 
night  ;  for  14  hours,  bring  it  to  2  •  and  so  on. 


ADAPTED    TO    WHITALL^S    PLANISPHERE. 

EXAMPLE. — a  Yirginis  (Spica),  R.  A.  13  hours,  16  minutes,  47  sccondj; 
turn  the  arrow  to  1  hour  16  minutes  past  midnight,  and  its  place  is  10 
deg.  19m.  5s.  south  of  the  equator.  (Page  83.) 

EXAMPLE. — a  Bo-o'tis  (Arcturus),  R.  A.  14  hours,  8  minutes,  22  seconds; 
turn  the  arrow  to  2  hours,  8  minutes,  22  seconds  past  midnight;  its  place 
will  be  under  the  20th  deg.  north  declination,  marked  on  the  meridian. 
(Page  88.) 

EXAMPLE. — a  Scorpii  (Antares),  R.  A.  16  hours,  19  minutes,  36  seconds; 
turn  the  arrow  to  4  hours,  19  minutes,  36  seconds  past  midnight,  and  its 
place  is  26  deg.  04m.  3s.  south  declination.  (Page  102.) 

EXAMPLE. — 61  Cygni,  the  most  remarkable  known  in  the  heavens,  R. 
A.  20  hours,  59  minutes,  43  seconds ;  declination  N".  37  deg.  58m. ;  is 
regarded  as  one  of  the  nearest  to  our  system.  (Page  126.)  Where  is  it  on 
the  Planisphere?  Ans.  In  Cygnus,  the  Swan. 

EXAMPLE. — A  gorgeous  cluster,  R.  A.  2  hours,  8  minutes,  58  seconds > 
declination  N.  56  deg.  24m. ;  is  one  of  the  most  magnificent  objects  in  the 
heavens.  (Page  37.)  "Where  is  it  ?  Ans.  In  the  sword-handle  of  Perseus. 

THE  RIGHT  ASCENSION  AND  DECLINATION  OF  THE  SUN,  MOON, 
PLANET,  STAR,  OR  COMET  BEING  GIVEN,  TO  FIND  ITS  PLACE  ON 
THE  PLANISPHERE. 

Bring  the  graduated  side  of  the  meridian  to  the  degrees  of 
right  ascension  marked  on  the  equator,  or  bring  the  hours  and 
minutes  of  R.  A.  opposite  the  arrow,  near  March  22d;  its  place 
will  be  under  the  declination  marked  on  the  meridian. 

EXAMPLE. — The  direction  of  the  sun  and  solar  system  is  towards  right 
ascension  259  deg.,  declination  north  35  deg.  In  what  constellation  is  that 
point  situated  ?  (571.)  Ans.  Hercules. 

EXAMPLE. — f\  Tauri  (Alcyone),  the  supposed  central  sun,  R.  A.  3  hours,  37 
minutes,  57  seconds;  declination  N.  23  deg.  36m.  Where  is  it?  (66.) 
Ans.  One  of  the  Pleiades. 

EXAMPLE.— What  star  has  R.  A.  18  hours,  31  minutes,  30  seconds;  de- 
clination N.  38  deg.  38m.  ?  (Page  115.)  Ans.  a  Lyra  (Vega). 

TO     FIND    THE     RIGHT     ASCENSION    AND    DECLINATION    OF    THE     SUN 
FOR   ANY    DAY    IN   THE    YEAR. 

The  Sun's  place  among  the  stars  is  on  the  ecliptic,  where 
the  day  of  the  month  is.  Bring  the  meridian  to  the  day  requir- 
ed. The  declination  will  be  found  on  the  meridian  opposite  the 
Oay,  and  the  degrees  of  right  ascension  on  the  equator,  under  the 


EXPLANATIONS    AND    PROBLEMS 

meridian ;    the  hours  and  minutes  opposite  the  arrow,  reading 
from  12  o'clock,  noon,  to  24  hours. 

"What  is  the  right  ascension  and  declination  of  the  sun  on  the  20th  of 
March  ?  (616.)  Ans.  0. 

What  is  the  right  ascension  and  declination  of  the  sun  on  the  21st  of 
June  ?  Ans.  90  deg.  or  6  hours  right  ascension,  23£  deg.  north  declination. 

"What  is  the  right  ascension  and  declination  of  the  sun  on  the  21st  of 
December?  Ans.  270  deg.  or  18  hours  right  ascension,  and  23^  deg.  south 
declination, 

On  what  day  of  the  month  does  the  sun  enter  each  of  the  signs?    (618.) 

Solution :  The  day  of  the  month  is  marked  opposite  each  sign  on  the 
ecliptic. 

What  is  the  declination  and  right  ascension  of  the  sun  on  the  5th  of 
June  ?  Ans.  22£  deg.  north  decimation,  73f  deg.  or  4  hours  55  minutes 
right  ascension. 

CHANGE    OF    SEASONS — DIFFERENT  LENGTHS  OF    DAYS  AND    NIGHTS. 

Bring  March  20th  on  the  ecliptic  to  the  east  horizon ;  at  March 
20th  on  the  outer  circle,  will  be  the  mean  time  of  the  sun's 
rising.  Bring  March  20th  to  west  horizon,  and  see  at  March 
20,  outside,  the  mean  time  of  the  sun's  setting.  The  rising  and 
setting  will  be  later  every  day  until  the  21st  of  June,  when  the 
days  decrease  until  December  21st.  (616  and  617.) 

AMONG  ALL  THE  STARS  VISIBLE  ON  A  CLEAR  EVENING,  WHICH  IS 
JUPITER  ?  WHICH  IS  SATURN,  OR  ANY  OTHER  OF  THE  PLANETS,  OR 
THE  MOON  ? 

Find  in  the  almanac  the  time  at  which  the  given  planet  rises, 
souths,  or  sets.  Bring  that  time  to  the  day  of  the  month ;  if  ris- 
ing, its  place  will  be  where  the  eastern  horizon  meets  the  ecliptic ; 
if  southing,  where  the  meridian  meets  the  ecliptic;  if  setting, 
where  the  western  horizon  meets  the  ecliptic.  Notice  its  place 
umong  the  stars,  and  then  bring  the  time  of  observation  to  the  day 
of  the  .month,  and  the  position  of  the  planet  in  the  heavens  will 
be  shown.  Or,  find  in  the  almanac  the  nearest  day  upon  which 
Vhe  pknet  is  in  conjunction  with  the  moon ;  and  find  the  POSI- 
TION OF  THE  MOON  on  that  day  in  like  manner,  which  will  bo 
nearly  the  place  of  the  planet  on  the  given  day. 

EXAMPLE. — Where  was  the  moon  at  7£  o'clock  on  the  evening 
18th,  1863? 


ADAPTED    TO    WHITALI/S   PLANISPHERE. 

Solution. — We  see  by  almanac  that  the  moon  southed  at  2  hours  58  minutc-b 
P.  M.  Bring  this  time  to  the  18th  of  August,  and  under  the  meridian  on 
the  ecliptic  12  deg.  in  the  sign  Libra,  constellation  Virgo,  will  be  the  moon's 
^lace  on  the  18th  of  August.  To  find  its  position  in  the  heavens,  bring  7-? 
o'clock  P.  M.  to  August  18th,  and  12  deg.  Virgo  (the  moon's  place)  will  bo 
about  an  hour  above  the  "W.  S.  W.  horizon. 

EXAMPLE. — Where  were  Saturn  and  Venus  at  the  above  time  ?  Ans.  By 
referring  to  the  almanac,  we  see  that  the/  were  in  conjunction  with  the 
tnoon. 

SIDEREAL    TIME. 

jBring  the  given  mean  (clock)  time  to  the  day  of  the  momn ; 
the  corresponding  sidereal  time  will  be  found  opposite  the 
arrow.  (392.) 

EXAMPLE. — August  18,  1863,  when  the  moon  is  on  the  meridian  at  2 
hours  58  minutes  P.  M.,  what  is  the  sidereal  tune  ?  Ans.  12  hours  46 
minutes.  The  right  ascension. 

EXAMPLE. — When  the  sun  is  on  the  meridian  December  22d,  what  is  the 
sidereal  time?  Ans.  18 hours  2m.  E.  A.  of  the  sun. 

EQUATION  OF  TIME.    TO  FIND  HOW  MUCH  THE  SUN  IS  FAST  OR  SLOW. 

Bring  the  meridian  to  the  given  day  on  the  ecliptic  ;  opposite 
the  same  day,  on  the  outer  circle,  will  be  the  time  the  sun  is  on  the 
meridian ;  if  before  12  o'clock,  the  sun  is  fast;  if  after  12  o'clock, 
the  sun  is  slow.  (397.) 

EXAMPLE. — Bring  the  meridian  to  November  10th,  on  the  ecliptic; 
opposite  that  date  will  be  found  11  hours  44  minutes,  the  sun  being  16 
minutes  fast. 

EXAMPLE. — Is  the  sun  fast  or  slow  September  1st?  how  much?  (397.) 
Ans.  Sun  and  clock  agree. 

EXAMPLE. — How  many  minutes  is  the  sun  slow  or  fast  on  the  10th  of 
February  ?  Ans.  14  minutes  slow. 

EXAMPLE. — When  the  sun  is  on  the  meridian  July  31st,  what  is  the  true 
clock  time  ?  Ans.  6  minutes  past  12. 

EXAMPLE. — How  shall  we  get  a  meridian  line  to-day  at  noon  ?  Ans. 
When  the  sun  is  on  the  meridian,  mark  its  shadow  for  the  meridian. 

TO  FIND  THB  VARIATION  OF    THE  MAGNETIC    NEEDLE,    OR  TO    GET    A 
MERIDIAN    LINE.       (46,     192-194.) 

Bring  the  meridian  to  17£°  on  the  equator,  the  arrow  will  point 
a'  1  hour  9  minutes,  the  right  ascension  of  the  north  pole  star  • 


EXPLANATIONS  A£D  PROBLEMS. 

opposite  the  day  of  every  month  will  be  found  the  time  the  north 
pole  star  is  on  the  meridian  ;  a  correct  range  at  that  time  will  be 
a  true  meridian.  Six  hours  after,  it  will  be  at  its  greatest  elonga- 
tion west ;  and  six  hours  later,  on  the  meridian  below  the  pole ; 
ind  six  hours  later,  at  it's  greatest  elongation  east. 

EXAMPLE. — At  what  time  can  we  get  a  meridian  line  December  10th? 
ins.  7  hours  50  minutes,  evening. 

EXAMPLE. — At  what  minute,  February  20th,  can  we  get  the  variation  of 
Lite  compass  ?  Ans.  6  minutes  past  3  in  the  morning. 

EXAMPLE. — When  will  the  polar  star  be  at  its  greatest  elongation  east 
August  23d  ?  Ans.  At  9  in  the  evening. 

TO     TELL     THE     COURSE    AND    POSITION    OP     THE     MILKY    WAY    ANY 
GIVEN    TIME. 

Bring  the  given  time  to  the  day  of  the  month  ;  the  course  and 
position  can  be  readily  traced  on  the  Planisphere.  (256-260.) 

"What  will  be  the  course  of  the  Milky  Way  on  the  5th  of  September, 
at  6,  9,  H  and  6  o'clock?  Ans.  At  6  o'clock  evening,  starting  from  northern 
horizon  to  east  of  zenith,  to  southern  horizon.  At  9  o'clock  it  appears  in 
the  N.  E.,  hi  zenith,  to  S.  "W.  At  H  o'clock  it  appears  in  the  east,  passes 
the  meridian  at  60  deg.  north,  to  the  west.  At  6  o'clock  morning,  it  appears 
hi  the  S.  E.,  passes  the  zenith  to  the  N.  W. 

TO  EXPLAIN  THAT  IN  SUMMER,  WHEN  THE  SUN  RUNS  HIGHEST,  THE 
FULL  MOON  RUNS  LOWEST  ;  AND  IN  WINTER,  WHEN  THE  SUN  RUNS 
LOWEST,  THE  FULL  MOON  RUNS  HIGHEST.  (421.) 

Bring  the  graduated  side  of  the  meridian  to  the  21st  of  June 
on  the  ecliptic,  the  sun's  place  among  the  stars  at  his  greatest  dis- 
tance north  ;  should  the  moon  full  on  that  day,  she  will  be  at  hei 
greatest  distance  south,  in  the  opposite  part  of  the  sky ;  shown  by 
bunging  the  meridian  to  the  21st  of  December  on  the  ecliptic,  at 
her  greatest  distance  south.  Bring  the  first  date  to  the  W.  N.  W. 
horizon,  and  the  second  date  will  be  near  the  E.  S.  E. ;  when  the 
sun  sets  at  his  greatest  distance  north  in  summer,  the  full  moon 
will  rise  at  her  greatest  distance  south. 

For  winter,  reverse  the  above,  by  bringing  the  second  date  near 
the  W.  S.  W.,  showing  the  sun's  setting  at  his  greatest  distance 
south,  while  the  full  moon  can  be  rising  in  the  E.  N.  E.,  at  her 
greatest  distance  nortti. 


By  the  almanac,  see  when  the  moon  is  full,  and  the  time  sne  la 
south,  by  which  find  her  place  on  the  Planisphere. 

Where  will  the  full  moon  of  June  be  found  ?  Ans.  At  her  greatest  dis- 
tance south. 

"Where  will  the  full  moon  in  December  be  found?  Ans.  At  her  greatest 
distance  north. 

The  Harvest-Moon  (626-635),  so  called  in  some  parts  of 
Europe,  is  of  great  benefit  to  the  husbandman,  by  lengthening  the 
day  while  gathering  the  fruits  of 'the  earth,  and  takes  place  at  the 
full  moon  in  September,  when  the  moon  rises  for  several  evenings 
near  the  same  hour.  Shown  on  the  Planisphere  by  bringing  6 
o'clock,  evening,  to  the  20th  day  of  September.  The  eastern 
horizon,  first  meridian,  ecliptic,  and  equator,  meet  at  the  vernal 
equinox.  Should  the  moon  be  full  on  that  day,  and  rise  at  the 
vernal  equinox  at  6,  on  the  following  evening  she  will  have  moved 
eastward  about  13  deg. ;  then  turn  the  horizon  until  13  deg.  on  the 
ecliptic  rises,  opposite  the  21st  day  of  September,  will  be  found  the 
time  of  the  moon's  rising  to  be  about  28  minutes  later.  Bring  13 
deg.  more  above  the  horizon,  opposite  the  22d  of  September,  will 
be  found  the  time  of  the  moon's  rising  to  be  about  28  minutes 
later.  The  ecliptic  being  nearly  parallel  to  the  horizon,  it  changes 
less  than  half  an  hour  per  night.  Now  turn  6  o'clock,  evening,  to 
March  22d,  the  eastern  horizon  meets  the  autumnal  equinox. 
Bring  13  deg.  of  the  ecliptic  up,  and  opposite  March  23d  will  be 
found  *7  o'clock,  making  more  difference  in  one  day  than  there 
was  before  shown  in  two  days ;  the  ecliptic  being  now  nearly 
perpendicular  to  the  horizon. 

See  in  the  almanac  the  day  the  moon  fulls  in  September ;  by 
her  southing  locate  her  on  the  Planisphere  ;  and  by  bringing  her 
place  to  the  eastern  horizon,  the  time  of  rising  can  be  seen  op- 
posite the  day  of  the  month.  Locate  the  moon  for  the  next  day 
and  note  the  difference  in  time  of  rising,  to  see  the  Harvest-MooD 
illustrated. 

TO    CONVERT    TIME    INTO    DEGREES,     OR    DEGREES    INTO    TIME. 

Bring  the. meridian  to  the  center  of  the  star.  The  degrees  of 
right  ascension  will  be  read  on  the  equator  or  equinoctial  opposite 
0  on  the  meridian.  The  arrow,  at  March  22d,  will  point  at  the 
hour  and  minute  of  R.  A.,  reading  from  12  noon  around  to  12 
noon,  counting  24  hours. 


EXPLANATIONS    AND    PROBLEMS 

EXAMPLE  2. — (Page  328.)  If  it  is  12  o'clock  at  this  place,  what  is  the  time 
20  deg.  east  of  us  ?  Bring  the  meridian  te  20  deg.  on  the  equinoctial,  and 
opposite  the  arrow  read  1  hour  20  minutes  past  12. 

EXAMPLE  4. — (Page  329.)  A  vessel  leaves  Boston,  and  having  been  tossed 
about  in  foul  weather  for  some  days,  finds,  that  when  it  is  1 2  o'clock  by 
the  sun,  it  is  only  11  o'clock  and  50  minutes  by  the  watch;  is  the  vessel 
east  or  west  of  Boston ;  and  how  many  degrees?  Ans.  2  deg.  30m.  east. 

TO    FIND  THE    AZIMUTH,  AMPLITUDE,  ZENITH    DISTANCE,  AND   VERTI- 
CAL CIRCLE  OF  A  STAR  AT  ANY  TIME. 

Bring  the  given  time  to  the  day  of  the  month ;  lay  a  straight 
edge  on  the  zenith;  let  it  pass  through  the  star  to  meet  the 
horizon ;  that  line  will  be  a  quarter  of  a  vertical  circle.  From 
the  east  or  west  which  is  nearest  to  the  line,  will  be  the  amplitude  ; 
from  the  horizon  to  the  star,  measured  on  the  vertical  line,  will  be 
the  altitude;  from  the  star  to  the  zenith,  will  be  the  zenith  dis- 
tance. 

[To  measure  the  azimuth  in  degrees,  we  know  that  a  circle  is 
360  cleg.:  from  N.  to  S.  will  be  180  de<r.,  from  S.  to  E.  90  deg., 
from  S.  to  S.  E.  45  deg.,  from  S.  to  S.  S.  E.  22£  deg.,  from  S.  to 
S.  by  E.  Hi.] 

TO  FIND    AT  WHAT    TIME    ANY    STAR   WILL  COME    TO  THE    MERIDIAN, 
OR  RISE,  OR  SET,  ON  ANY  GIVEN  DAY  OF  THE  MONTH. 

Turn  the  graduated  side  of  the  meridian,  or  the  eastern  or 
western  horizon,  to  the  center  of  the  star ;  opposite  the  day  of 
the  month  will  be  found  the  time  required. 

EXAMPLE. — At  what  time  will  a  Gemini  (Castor)  culminate,  on  the  24th 
of  February?  (95.)  Ans.  About  9  o'clock. 

TO  FIND   ON  WHAT    DAY  OF    THE    YEAR  ANY  STAR  PASSES    THE  MERI- 
DIAN, Oil    RISES,  OR  SETS,  AT  ANY  GIVEN  TIME. 

Bring  the  meridian,  or  the  eastern  or  western  horizon,  to  the 
centre  of  the  star ;  opposite  the  given  time  will  be  found  the  day 
required. 

EXAMPLE  — On  what  *lny  will  a  Leo  (Reg'-u-lus)  be  on  the  meridian  about. 
5  o'clock?  (124.)  Ana  April  Gtn. 


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FORM  NO.  DD6,  60m,  1  1  778          BERKELEY,  CA  94720 


Burritt 

TVna      eft 


raphy  of  the 


heavens 


M530304 


